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MARVELS OF POND-LIFE.
MARVELS
OF
P 0 O-lIFE;
OR, A
YEAR’S MICROSCOPIC RECREATIONS
AMONG THE
POLYPS, INFUSORIA, ROTIFERS, WATER-BEARS, AND
POLYZOA.
BY HENRY J. SLACK, E.G.S.,
AUTHOR OF “THE PHILOSOPHY OF PROGRESS IN HUMAN AFFAIRS,” ETC., ETC.
LONDON:
GROOMBRIDGE AND SONS.
M DCCC LX I.
INTRODUCTION.
As this little book is intended to be no more than an introduction to an agreeable branch of microscopical study, it is to be hoped it will not require a formal preface; but a few words may be convenient to indicate its scope and purpose.
The common experience of all microscopists con¬ firms the assertion made by Dr. Goring, that the most fascinating objects are living creatures of sufficient dimensions to be easily understood with moderate magnification ; and in no way can objects of this description be so readily obtained, as by devoting an occasional hour to the examination of the little ponds which are accessible from almost any situation. A complete volume of pond lore would not only be a bulky book — much bigger than the aldermanic tomes which it is the fashion to call “Manuals,” although the great stone fists in the British Museum would be required to grasp them comfortably, — but its composition would overtask all the philosophers of our day. In good truth, a tea-spoonful of water from a prolific
VI
INTRODUCTION.
locality often contains a variety of living forms, every one of which demands a profound and pa¬ tient study, if we would know but a few things concerning it.
To man, then, is a vast and a minute. Our minds ache at the contemplation of astronomical immensities, and we are apt to see the boundless only in prodigious masses, countless numbers, and immeasurable spaces. The Creative Mind knows no such limitations; and the microscope shews us that, whether the field of nature’s operation be what to our apprehension is great or small, there is no limit to the exhibition of marvellous skill. If the “undevout astronomer” be umad,” the un- devout microscopist must be still more so, for if the matter be judged by human sense, the skill is greater as the operation is more minute; and not the sun itself, nor the central orb round which he revolves, with all his attendant worlds, can furnish sublimer objects of contemplation, than the miraculous assemblage of forces which make up the life of the smallest creature that the microscope reveals.
There is an irresistible charm in the effort to trace beginnings in nature. We know that we can never succeed; that each discovery, which conducts back towards some elementary law or principle, only indicates how much still lies behind it: but
INTRODUCTION.
Yll
the geologist nevertheless loves to search out the first or oldest traces of life upon our globe; and so the microscopist delights to view the simplest exhibitions of structures and faculties, which reach their completion in the frame and mind of man. That one great plan runs through the whole uni¬ verse is now an universally accepted truth, and when applied to physiology and natural history, it leads to most important results.
The researches of recent philosophers have shewn us that nature cannot be understood by studying the parts of animals with reference merely to their utility in the economy of the creature to which they belong. We do, indeed, find an admirable correspondence between structures and the services they perform; but every object in creation, and every part of it, is in harmonious relation to some grand design, and exhibits a conformity to some general mode of operation, or some general disposition and direction of forces, which secures the existence of the individual or the species, and at the same time works out the most majestic schemes. Microscopic researches, such as are within the reach of millions, offer many of the most beautiful illustrations of these truths; and although the following pages are confined to such objects as are easily obtainable from ponds, and relate almost exclusively to the Infusoria, the Rotifers,
V11L
INTRODUCTION.
the Polyps, and the Polyzoa, it is hoped that they will assist in associating a few of the highly suggestive reasonings of science, with one of the most pleasurable recreations that human ingenuity has devised.
After a preliminary chapter, which is intended to assist the young microscopist in some technical matters, that could not be conveniently introduced into the text, the observations are distributed in chapters, corresponding with the twelve calendar months. This arrangement was suggested by the author’s diary of operations for the year 1860, and although it by no means follows that the months in which particular creatures were then discovered, will be those in which they will be most readily found in other years, it was thought advantageous to give a real account of an actual period of microscopic work, and also that the plan would facilitate a departure from the dry manner of a technical treatise. The index will enable any one to use the book for the purpose of reference, and it will be observed that the first, chapter in which any member of a group of creatures is in¬ troduced, is that in which a general description of the class is given. The illustrations are taken from drawings made by the wife of the author from the actual objects, with the exception of a few instances, in which the authority is acknowledged.
INTRODUCTION.
IX
The ponds referred to are all either close to, or within a moderate distance of, London; but similar objects will in all probability be obtained from any ponds similarly situated, and the des¬ criptions and directions given for the capture of the minute prey will be found generally applicable. Care has been taken throughout to explain the most convenient methods of examining the objects, and although verbal descriptions are poor substitutes for the teachings of experience, it is hoped that those here given will remove some difficulties from a pursuit that no intelligent person can enter upon without pleasure, or consent to abandon when its elementary difficulties have been mastered, and the boundless fields of discovery are opened to view. Let not the novice be startled at the word “discovery.” It is true that few are likely to
arrive at new principles or facts which will inscribe their names upon the roll of fame; but no one
of ordinary powers can look at living objects
with any considerable perseverance, without seeing much that has never been recorded, and which is nevertheless worthy of note; and when the mind, by its own exertions, first arrives at a knowledge of new truth, an emotion is felt akin to that
which more than recompenses the profoundest philosopher for all his toil.
CONTENTS.
CHAPTER I.
MICROSCOPES AND THEIR MANAGEMENT.
PAGE
Powers that are most serviceable — Estimated by Focal length — Length of Body of Microscope and its Effects — Popular Errors about Great Magnification — Modes of Stating Magnifying Power — Use of an “Erector” — Power of various Objectives with different Eye-pieces — Examination of Surface Markings — Methods of Illumination — Direct and Oblique Light — Stage Aperture — Dark-ground Illumina¬ tion — Mode of Softening Light — Microscope Lamps — Care of the Eyes. ......... 1
CHAPTER
II.
.JANUARY.
Visit to the Ponds — Confervpe — Spirogyra quinina — Vorticella — Common Rotifer — Three Divisions of Infusoria — Phy- tozon — Protozoa — Rotifera — Tardigrada — Meaning of these Terms — Euglense — Distinction between Animals and Vege¬ tables — Description of Vorticelhe — Dark-ground lllumina-
Xll
CONTENTS.
TAGE
tion — Modes of producing it — The Nucleus of the Vorti- cella — Methods of Reproduction — Ciliated Protozoa — Wheel-bearers or Rotifers — Their Structure — The Common Rotifer — The young Rotifer seen inside the old one — An Internal Nursery — “Differentiation” and “Specialization” — Bisexuality of Rotifers — Their Zoological Position — Diver¬ sities in their Appearance — Structure of their Gizzard — Description of Rotifers. ....... 15
CHAPTER III.
FEBRUARY.
Visit to Hampstead — Small Ponds — Water-Fleas — Water- Beetle — Snails — Polyps — Hydra viridis — The Dipping- tube — A Glass Cell — The Hydra and its Prey — Chydorus Sphsericus and Canthocamptus, or Friends and their Escapes — Cothurnia — Polyp Buds — Catching Polyps — Mode of Viewing Them — Structure of Polyps — Sarcode — Polyps Stimulated by Light — Are they Conscious? — Tentacles and Poison Threads — Paramecium — Trachelius — Motions of Animalcules, whether Automatic or directed by a Will —
Their Restless Character. ....... 41
CHAPTER IV.
MARCH.
Paramecia — Effects of Sunlight — Pterodina patina — Curious Tail — Lise of a Compressorium — Internal Structure of Pterodina — Metopidia — Trichodina pediculus — Cothurnia — alpina — Its Three-sided Box — Protrusion of its Gizzard Mouth. .
CONTEXTS.
X1U
PAGE
CHAPTER V.
APRIL.
Tlie Beautiful Floscule — Mode of seeking for Tubicolar Rotifers — Mode of Illuminating the Floscule — Difficulty of seeing the Transparent Tube — Protrusion of Long Hairs — Lobes — Gizzard — Hairy Lobes of Floscule not Rotatory Organs — Glass Troughs — Their Construction and Use — Movement of Globules in Lobes of Floscule — Chaetonotus larus — Its Mode of Swimming — Coleps hirtus — Devourer of Dead Entomostraca — Dead Rotifer and Vibriones — Theories of Fermentation and Putrefaction — Euplotes and Stylonichia — Fecundity of Stylonichia. . . . .71
CHAPTER VI.
MAY.
Floscularia cornuta — Euchlanis triquetra — Melicerta ringens — Its Powers as Brick-maker, Architect, aud Mason —
Mode of Viewing the Melicerta — Use of Glass Cell — Habits of Melicerta — Curious Attitudes — Leave their Tubes at Death — Carchesium — Epistylis — Their Elegant Tree Forms — A Parasitic Epistylis like the “Old Man of the Sea” — Halteria and its Leaps — Aspidisca lynceus. . . .89
CHAPTER VII.
JUNE AND JULY.
Lindia torulosa — (Ecistes crystallinus — A Professor of Deport¬ ment on Stilts — Philodina — Changes of Form and Habits — Structure of Gizzard in Philodina Family — Mr. Gosse’s
XIV
CONTENTS.
PAGE
Description — Motions of Rotifers — Indications of a Will — Remarks on the Motions of Lower Creatures — Various Theories — Possibility of Reason — Reflex Actions — Brain of Insects — Consensual Actions — Applications of Physiological Reasoning to the Movements of Rotifers and Animalcules. 99
CHAPTER VIII.
AUGUST.
Mud Coloured by Worms — Their Retreat at Alarm — A Country Duck-Pond — Contents of its Scum — Cryptomonads — Their Means of Locomotion — A Triarthra (Three-limbed Rotifer) — The Brachion or Pitcher Rotifer — Its Striking Form — Enormous Gizzard — Ciliary Motion inside this Creature — Large Eye and Brain — Powerful Tail — Its Functions — Eggs. ........ 113
CHAPTER IX.
SEPTEMBER.
Microscopic Value of Little Pools — Curious Facts in Ap¬ pearance and Disappearance of Animalcules and Rotifers — Mode of Preserving them in a Glass Jar — Fragments of Melicerta Tube — Peculiar Shape of Pellets — Amphileptus — Scaridium longicaudum — A Long-tailed Rotifer — Stephan- oceros Eichornii — A Splendid Rotifer — Its Gelatinous Bottle — Its Crown of Tentacles — Retreats on Alarm — Illumination Requisite to see its Beauties — Its Greediness — Richly-coloured Food — Nervous Ganglia. . . . 127
CHAPTER X.
OCTOBER.
S ten tors and Stephanoceri — Description of Stentors — Mode of viewing them — Their Abundance — Social Habits — Soli¬ tary Stentors living in Gelatinous Caves — Propagation by
CONTENTS.
XV
Divers Modes — Limnias ceratopliylli — Another Tube- dwelling Rotifer — Young and Old Specimens — A Group of Vagiuicoke — Changes of Shape — A Bubble-blowing Vor- 0 cell a. •••••••••••
CHAPTER XI.
NOVEMBER.
Characteristics of the Polyzoa — Details of Structure according to Allman — Plumatella repens — Its Great Beauty under proper Illumiuation — Its Tentacles and their Cilia — The Mouth and its Guard or Epistome — Intestinal Tube — How it swallowed a Rotifer, and what happened — Curiosities of Digestion — Are the Tentacles capable of Stinging? — Rest¬ ing Eggs, or “Statoblasts” — Tube of Plumatella — Its Muscular Fibres — Physiological Importance of their Structure. ..........
CHAPTER XII.
DECEMBER.
Microscopic Hunting in Winter — Water-Bears, or Tardigrada Their Comical Behaviour — Mode of viewing them — Sin¬ gular Gizzard — Wenham’s Compressorium — Achromatic Condenser — Mouth of the Water-Bear — Water-Bears' Exposure to Heat — Soluble Albumen — Physiological and Chemical Reasons why they are not killed by Heating or Drying — The Trachelius ovum — Mode of Swimming — Method of Viewing — By Dark-ground Illumination — Cu¬ rious Digestive Tube with Branches — Multiplication by Division — Change of Form immediately following this Process — Subsequent Appearances. .
CHAPTER XIII.
Conclusion. — Remarks on Classification, etc.
TAGE
141
155
169
185
LIST OF ILLUSTRATIONS.
JANUARY. — Chapter II.
FACE
Euglenas . 21
AMrticell.e . 29, 30, 31, 32
Rotifer vulgaris . 33
Gizzard of Rotifer . 38
FEBRUARIL — Chapter III.
Stinging Organs of Polyp . 45, 47, 4S
Anguillula stung by Polyp . 52
Paramecium . 54
MARCH.— Chapter IY.
Pterodina patina . GO
Gizzard of Pterodina . 01
Tail of Patina . 02
Metopidia . 05
Trichodina pediculus . . . . 65
CoTHURNIA IMBERBIS . 07
Salpina redunca . . . . . . . . .70
APRIL.— Chapter Ar.
Floscularia ornata ........ 73
Ch^etonotus larus . 83, 84
CoLEPS HIRTUS . . . 85
Euplotes patella ......... 80
Stylonichia . . 80
XV111
LIST OF ILLUSTRATIONS.
MAY. — Chapter YI.
Melicerta ringens . 91
Epistylis .......... 95
Carchesium . 96
JUNE AND JULY.— Chapter YII.
(Ecistes crystallinus . 102
Philodina . 104-5
AUGUST.— Chapter VIII.
Crypto monads ......
Triarthka .......
Brachions .......
SEPTEMBER.— Chapter IX.
SCARIDIUM LONGICAUDUM . 133
S l’EPH ANOCEROS EICHORNII ....... 135
OCTOBER. — Chapter X.
Stentors . . 145
Limn ias ceratophylli ....... 149
Vagin i cola . 152
117-18 . 120 122
NOVEMBER. — Chapter XI.
Plumatella repens . 159
“ “ (Single Polypide enlarged) . . . 163
DECEMBER,— Chapter XII.
W ater-Bear Trachelius ovum
. 173 180, 183
DESCRIPTION OF FRONTISPIECE.
The large object in the middle is a Stentor poly- morphus, magnified one hundred and five diameters; hanging from the top are \ orticelhe, magnified about sixty diameters; on each side at the bottom are Polyps, (Hydra viridis and vulgaris,) the latter having pro¬ duced by budding a young one as large as herself. These are slightly magnified, the natural size of the objects in fine specimens similarly extended, measures about half an inch. The border is composed of Ana- cliaris alsinastrum, a weed often prolific in microscopic forms.
CHAPTER I.
MICROSCOPES AND THEIR MANAGEMENT.
POWERS THAT ARE MOST SERVICEABLE— ESTIMATED BY FOCAL LENGTH— LENGTH OF BODY OF MICROSCOPE AND ITS EFFECTS— POPULAR ERRORS ABOUT GREAT MAGNIFICATION —MODES OF STATING MAGNIFYING POWER— USE OF AN “ ERECTOR”— POWER OF VARIOUS OBJECTIVES WITH DIF¬
FERENT EYE-PIECES— EXAMINATION OF SURFACE MARKINGS
—METHODS OF ILLUMINATION— DIRECT AND OBLIQUE LIGHT —STAGE APERTURE— DARK GROUND ILLUMINATION— MODE OF SOFTENING LIGHT— MICROSCOPE LAMPS-CARE OF THE
EYES.
/*■
B
MARVELS OF POND-LIFE
CHAPTER I.
PLAIN HINTS ON MICROSCOPES AND THEIR
MANAGEMENT.
The microscope is rapidly becoming the com¬ panion of every intelligent family that can afford its purchase, and, thanks to the skill of our op¬ ticians, instruments which can be made to answer the majority of purposes, may be purchased for three or four guineas, while even those whose price is counted in shillings are by no means to be despised. The most eminent English makers stand unrivalled throughout the world, while the average productions of respectable houses exhibit so high a degree of excellence, as to make comparisons invidious. We shall not, therefore, indulge in the praises of par¬ ticular firms, but simply recommend any reader entering upon microscopic study, to procure an achromatic instrument, if it can be afforded, and
4
MARVELS OF POND-LIFE.
having at least two powers, one with a focus of an inch or two-thirds of an inch, and the other of half or a quarter. Cheap microscopes have usually only one eye-piece, those of a better class have two, and the best are furnished with three, or even more.
The magnifying power of a compound microscope depends upon the focal length of the object-glass, (or glass nearest the object,) upon the length of the tube, and the power of the eye-piece. With regard to object-glasses, those of shortest focal length have the highest powers, and the longest eye-pieces have the lowest powers. The body of a microscope, or principal tube of which it is com¬ posed, is, in the best instruments, about nine inches long, and is furnished with a draw tube, capable of being extended six inches more. From simple optical principles, the longer the tube the higher the power obtained with the same object-glass; but only object-glasses of very perfect construction will bear the enlargement of their own imperfections, which results from the use of long tubes; and con¬ sequently for cheap instruments the opticians often limit the length of the tube, to suit the capacity of the object-glasses thev can afford to give for the money. Such microscopes may be good enough for the generality of purposes, but they do not, with glasses of given focal length, afford the same
O O O 7
POPULAR ERRORS ABOUT GREAT MAGNIFICATION.
5
magnifying power as is done by instruments of better construction. The best and most expensive glasses will not only bear long tubes, but also eye¬ pieces of high power, without any practical diminu¬ tion of the accuracy of their operation, and this is a great convenience in natural history investiga¬ tions. To obtain it, however, requires such perfec¬ tion of workmanship, as to be incompatible with cheapness. An experienced operator will not be satisfied without having an object-glass at least as high as a quarter, that will bear a second eye¬ piece, but beginners are seldom successful with a higher power than one of half-inch focus, or there¬ abouts, and before trying this, they should familiarize themselves with the use of one with an inch focus.
It is a popular error to suppose that enormous magnification is always an advantage, and that a microscope is valuable because it makes a flea look as big as a cat or a camel. The writer has often smiled at the exclamations of casual visitors, who have been pleased with his microscopic efforts to entertain them. “Dear me, what a wonderful instrument; it must be immensely powerful;” and so forth. These ejaculations have often followed the use of a low power, and their authors have been astonished at receiving the explanation that the best microscope is that which will shew the most with the least magnification, and that ac-
6
MARVELS OF POND-LIFE.
curacy of definition, not increase of bulk, is the great thing needful.
o cr
Scientific men always compute the apparent en¬ largement of the object by one dimension only. Thus, supposing an object one-hundredth of an inch
square were magnified so as to appear one inch
\
square, it would, in scientific parlance, be magnified uoue hundred diameters, ” or one hundred linear; and the figures 100 would be appended to any drawing which might be made from it. It is, however, obvious that the length is magnified as well as the breadth ; and hence the magnification of the whole surface, in the instance specified, would be one hundred times one hundred, or ten thousand; arid this is the way in which magnification is popularly stated. A few moments’ consideration will shew that the scientific method is that which most readily affords information. Any one can instantly comprehend the fact of an object being made to look ten times its real length; but if told that it is magnified a hundred times, he does not know what this really means, until he has gone through the process of finding the square root of a hun¬ dred, and learnt that a hundredfold magnification means a tenfold magnification of each superficial dimension. If told, for example, that a hair is magnified six hundred diameters, the knowledge is at once conveyed that it looks six hundred times
USE OF AN ERECTOR.
7
as broad as it is; but a statement that the same hair is magnified three hundred and sixty thousand times, only excites a gasping sensation of wonder, until it is ascertained by calculation that the big figures only mean what the little figures instantly express. In these pages the scientific plan will always be followed.
If expense is not an object, it is well to be provided with an object-glass as low as two or three inches focus, which will allow the whole of objects, having the diameter of half an inch or more, to be seen at once. Such a low power is exceedingly well-adapted for the examination of living insects, or of the exquisite preparations of entire insects, which can now be had of all op¬ ticians. Microscopes which have a draw tube can be furnished with an erector , an instrument so called because it erects the images, which the microscope has turned upside down, through the crossing of the rays. This is very convenient for making dis¬ sections under the instrument; but it also gives us the means of reducing the magnifying power of an object-glass, and thus obtaining a larger field. The erector is affixed to the end of the draw tube, and by pulliug it out, or thrusting it in, the rays from the object-glass are intercepted at different distances, and various degrees of power obtained. As it is only the object of this preliminary chapter
8
MARVELS OF POND-LIFE.
to give a little general information, special pieces of apparatus to use with a microscope will not be described, but the most necessary will be introduced in the following chapters, and the mode of using them explained.
Beginners will be glad to know how to obtain the magnifying power which different objects re¬ quire, and it may be stated that with a full-sized microscope, a two-inch object-glass magnifies about twenty-five diameters with the lowest eye-piece; a one-inch object-glass, or two-thirds, from fifty to sixty diameters; a half-inch about one hundred; a quarter-inch about two hundred. The use of higher eye-pieces adds very considerably to the power, but in proportions which differ with different makers. The instrument used by the writer has three eye¬ pieces, giving with a two-thirds object-glass, powers of sixty, one hundred and five, and one hundred and eighty respectively ; and with a fifth two hun¬ dred and forty, four hundred and thirty, and seven hundred and twenty, which can be augmented by the use of the draw tube. When an instrument is bought, the optician should be requested to give a table of the action of its object-glasses and eye¬ pieces, and there will then be no difficulty in selecting the combination necessary to follow the observations of others. When it is desired to examine delicate surface markings of extreme mi-
METHODS OF I U. T MIN ATION.
9
nuteness, high powers should he obtained by the employment of object-giasses of short focus, and low eye-pieces; but for ordinary purposes an ob¬ ject-glass may be used with any eye-piece with which it will give a clear, well-lit, and distinct- looking image.
It has been well observed that the illumination of objects is quite as important as the glasses that are employed, and the most experienced microscopists have never done learning in this matter. Most microscopes are furnished with two mirrors beneath the stage, one plane and one concave. The first will throw a few parallel rays through any trans¬ parent object properly placed, and the latter causes a number of rays to converge, producing a more powerful effect. The first is usually used in day¬ light, when the instrument is near a window, (one with a north aspect, out of direct sunlight, being the best;) and the second is commonly employed when the source of illumination is a candle or a lamp. By varying the angle of the mirror the light is thrown through the object more or less obliquely, and its quantity should never be sufficient to pain the eye. Few objects are seen to the best advantage with a perfectly direct light, and the beginner should practise till the amount of incli¬ nation is obtained which produces the best effect.
It is advisable that the hole in the stage of
10
MARVELS OF POND-LIFE.
the microscope should he large — at least an inch and a half each wav — so tlWt the entrance of oblique rays is not obstructed, and it is desirable that the mirror, in addition to sliding up and down, should have an arm by which it can be thrown completely out of the perpendicular plane of the body of the instrument. This enables such oblique rays to be employed as to give a dark field, all the light which reaches the eye, being refracted by the object through which it is sent. The opticians sell special pieces of apparatus for this purpose, but though they are very useful, they do not render it less desirable to have the mirror mounted as described.
Most microscopes are furnished with a revolving diaphragm, with three holes, of different sizes, to diminish the quantity of light that is admitted to the object. This instrument is of some use, and offers a ready means of obtaining a very soft agree¬ able light for transparent objects, viewed with low powers. For this purpose cut a circular disk of India or tissue paper, rather larger than the biggest aperture; scrape a few little pieces of spermaceti, and place them upon it, then put the whole on a piece of writing-paper, and hold it a few inches above the flame of a candle, moving it gently. If this is dexterously done, the spermaceti will be melted without singing the paper, and when it is cold the disk will, be found transparent. Place it
M U'HOSCOrK LAMPS.
11
over the hole in the diaphragm, send the light through it, and the result will be a very soft agreeable effect, well suited for many purposes, such as viewing sections of wood, insects mounted whole, after being rendered transparent, many small water creatures, etc. Another mode of accomplishing this purpose is to place a similarly prepared disk of paper on the flat side of a bull’s-eye lens, and transmit the light of a lamp through it. This plan may be used with higher powers, and the white opaque light it gives may be directed at any angle by means of the mirror beneath the stage.
An ordinary lamp may be made to answer for microscopic use, but one of the small paraffine lamps, now sold everywhere for eighteen-pence, is singularly convenient. It is high enough for many purposes, and can easily be raised by one or more books. That used by the writer has a small silvered reflector behind the flame, which is serviceable when much light is required.
Many people fancy that the eyes are injured by continual use of the microscope, but this is far from being the case if reasonable precautions are taken. The instrument should be inclined at a proper angle, all excess of light avoided, and the object brought into focus before it is steadily looked at. Most people solemnly shut one eye
MARVELS OF POND-LIFE.
13
before commencing a microscopic examination; this is a practical and physiological mistake. Nature meant both eyes to be open, and usually resents a prolonged violation of her intentions in this mat¬ ter. It requires but a little practise to keep both eyes open, and only pay attention to what is seen by that devoted to the microscope. The acquisition of this habit is facilitated, and other advantages gained, by a screen to keep out extra¬ neous light. For this purpose take a piece of thin cardboard about nine inches square, and cut a round hole in it, just big enough to admit the tube of the microscope, about two inches from the bottom, and equidistant from the two sides. Next cut off the two upper corners of the cardboard, and give them a pleasant-looking curve. Then cover the cardboard with black velvet, the commonest, which is not glossy, answers best, and your screen is made. Put the hole over the tube of the microscope, and let the screen rest on the little ledge or rim which forms an ornamental finish to most instruments. A piece of cork may be gummed at the back of the screen, so as to tilt it a little, and diminish its chance of coming into contact with that important organ the nose. This little contrivance adds to the clearness and brilliancy of objects, and is a great accommodation to the
eves.
CARE OF THE EYES.
13
One more oculistic memorandum, and we have done with this chapter. Do not stare at portions of objects that are out of focus, and consequently indistinct, as this injures the eyes more than any¬ thing. "Remember the proverb, “None so deaf as. those that won’t hear.” which naturally suggests for a companion, uNone so blind as those that won’t see.” It is often impossible to get every object in the field in focus at one time:— look only at that which is in focus, and be blind to all the rest. This is a habit easily acquired, and is one for which our natural microscopes are exceedingly grateful; and every judicious observer desires to keep on the best terms with his eyes.
CHAPTER IT.
JANUARY.
VISIT TO THE PONDS — CONFERVA — SPIROGYRA QUININA— VORTICELLA— COMMON ROTIFER— THREE DIVISIONS OF IN¬ FUSORIA— PHYTOZOA — PROTOZOA— ROT1FERA — TARDIGRADA —MEANING OF THESE TERMS — EUGLENA — DISTINCTION BE¬ TWEEN ANIMALS AND VEGETABLES- DESCRIPTION OF VORTICELLA— DARK GROUND ILLUMINATION— MODES OF PRODUCING IT— THE NUCLEUS OF THE VORTICELLA— METHODS OF REPRODUCTION- CILIATED PROTOZOA— WHEEL BEARERS OR ROTIFERS— THEIR STRUCTURE— THE COMMON ROTIFER— THE YOUNG ROTIFER SEEN INSIDE THE OLD ONE— AN INTERNAL NURSERY— “DIFFERENTIATION” AND “SPECIAL¬ IZATION”— BISEXUALITY OF ROTIFERS— THEIR ZOOLOGICAL
POSITION— DIVERSITIES IN THEIR APPEARANCE— STRUCTURE OF THEIR GIZZARD— DESCRIPTION OF ROTIFERS.
CHAPTER II.
JANUARY.
The winter months are on the whole less fa¬ vourable to the collection of microscopic objects from ponds and streams, than the warmer portions of the vear; but the difference is rather in abundance than in variety, and with a very moderate amount of trouble, representatives of the principal classes
can alwavs be obtained.
%}
On a clear January morning, when the air was keen, but no ice had yet skinned over the surface of the water, a visit to some small ponds in an open field, not far from Kentish Town, provided entertainment for several days. The ponds were selected from their open airy situation, the general clearness of their water, and the abundance of ve¬ getation with which they were adorned. Near the margin, confervas abounded, their tangled masses of hair-like filaments often matted together, almost with the closeness of a felted texture. At inter¬ vals, minute bubbles of air, with occasionally a few of greater size, indicated that the complex processes
18
MARVELS OF POND-LIFE.
of vegetable life were actively going on, that the tiny plants were decomposing carbonic acid, dex¬ terously combining the carbon — which we are most familiar with in the black opaque form of charcoal — to form the substance of their delicate translucent tissues, and sending forth the oxygen as their contribution to the purification of the adjacent water, and the renovation of our atmospheric air. This was a good sign, for healthy vegetation is favourable to many of the most interesting forms of infusorial life. Accordingly the end of a walking-stick was inserted among the green threads, and a skein of them drawn up, dank, dripping, and clinging together in a pasty-looking mass. To hold up a morsel of this mess, and tell some one, not in the secrets of pond-lore, that its dripping threads were objects of beauty, surpassing human produc¬ tions, in brilliant colour and elegant form, would provoke laughter, and suggest the notion that you were poking fun at them, when you poked out your stick with the slimy treasure at its end. But let us put the green stuff into a bottle, with some water from its native haunt, cork it up tight, and carry it away for quiet examination under the mi¬ croscope at home.
Here we are with the apparatus ready. We have transferred a few threads of the conferva from the bottle to the live box , spreading out the fine
VORTICELLJE.
19
fibres with a needle, and adding a drop of water. The cover is then gently pressed down, and the whole placed on the stage of the microscope, to be examined with a power of about sixty. A light is thrown somewhat obliquely by the mirror through the object, the focus adjusted, and a beautiful sight rewards the pains. Our mass of conferva turns out to contain one of the most elegant species. Fine hair-like tubes of an organic material, as transparent as glass, are divided by partitions of the same substance into cylindrical cells, through which a slender ribbon of emerald green, spangled at intervals with small round expansions, is spirally wound. We shall call it the Spiral Conferva, its scientific name being Spirogyra quinina. Some other species, though less elegantly adorned, make a pleasing variety in the microscopic scene; and appended to some of the threads is a group of small crystal bells, which jerk up and down upon spirally twisted stalks. These are the “Bell Flower Animalcules” of old observers, the Vorticellce , or Little Vortex-makers of the present day. Other small creatures flit about with lively motions, and among them we observe a number of green spindles that continually change their shape, while an odd¬ looking thing crawls about, after the manner of certain caterpillars, by bringing his head and tail together, shoving himself on a step, and then re-
MARVELS OF POND-LIFE.
20
peating the process, and making another move. He lias a kind of snout, behind which are two little red eyes, and something like a pig-tail sticks out behind. This is the Common Wheel-bearer, Rotifer vulgaris , a favourite object with microscopists, old and young, and capable, as we shall see, of doing something more interesting than taking the crawl we have described.
A higher power, say one or two hundred, may be conveniently applied to bring out the details of the inhabitants of our live box more completely; but if the glasses are good, a linear magnification of sixty will shew a great deal, with the advan¬ tage of a large field, and less trouble in following
O O " O
the moving objects of our search.
Having commenced our microscopic proceedings
by obtaining some Euglenae, Vorticellse, and a Rotifer, we are in a position to consider the chief charac¬ teristics of three great divisions of infusoria, which will often engage our attention.
o o
It is well known that animalcules and other small forms of being, may be found in infusions of hay or other vegetable matter, and hence all such and similar objects were called Infusoria by early observers. Many groups have been separated from the general mass comprehended under this term, and it is now used in various senses. The authors of the “Micrographic Dictionary” employ it
TIIRKE DIVISIONS OF INFUSORIA.
01
•v JL
to designate “a class of microscopic animals not furnished with either vessels or nerves, but exhibiting internal spherical cavities, motion effected by means of cilia, or variable processes formed of the sub¬ stance of the body, true legs being absent.” The objection to this definition is, that it to some extent represents theories which may not be true. That nerves are absent all through the class is an as¬ sumption founded merely upon the negative evidence of their not having been discovered, and the com¬ plete absence of “vessels” is still a contested point.
In the last edition of “Pritchard’s Infusoria,” to
which some of our ablest naturalists have contributed,
after separating two groups, the Desmids and the
Diatoms, as belonging to the vegetable world, the
remainder of the original family of infusoria are
classified as Phytozoa , Protozoa , Rotifer a, and Tar -
£
digrada. We shall explain these hard names imme¬ diately, first remarking that the Desmids and the Diatoms, concerning whom we do not intend to speak in these pages, are the names of two groups, one distinctly vegetable, while the other, although generally considered so, is yet held by some au¬ thorities to be in realitv animal. The Desmids
J
occur very commonly in water. We have some among our Confer vse. They are mostly brilliant green, and often take forms of a more angular and crystalline character than are exhibited by
MARVELS OF POND-LIFE.
higher plants. The Diatoms are still more common, and we see before us in our water-drop, some of their simplest representatives in the form of minute boats made of silica (hint,) and moved by means which no one can explain.
Leaving out the Desmids and Diatoms, ive have said that in Pritchard’s arrangement the views of those writers are adopted who divide the rest of the infusoria into four groups, distinguished with foreign long- tailed names, which we will translate and expound. First come the Phytozoa , under which we recognise our old acquaintance zoophyte turned upside down. Zoophytes mean animal-plants, Phytozoa mean plant-animals. We shall have by- and-bye to speak of some of the members of this artificial and unsatisfactory group, and postpone to that time a learned disquisition on the difference betweefi animals and plants, a difference observable enough if we compare a hippopotamus with a cab¬ bage, but which “grows small by degrees, and beautifully less,” as we contemplate lower forms.
After the Phytozoa come the Protozoa , or first forms in which animality is distinctly recognised. Under this term are assembled creatures of very various organization, from the extreme simplicity of the Proteas or Amceha , a little lump of jelly, that moves by thrusting out portions of its body, so as to make a sort of extempore legs, and in which
WATER BEARS.
no organs can be discerned, up to others that are highly-developed, like our Vorticelloe. This group is evidently provisional, and jumbles together objects that may be widely separated when their true structure and real affinities are discerned.
Following the Protozoa , come the Rotifer a, or Wheel-bearers, of which we have obtained an ex¬ ample from our pond, and whose characteristics we shall endeavour to delineate when our specimen is under view: and last in the list we have the Tar- digrada , uSlow-steppers,” or Water Bears, queer little creatures, something like new-born puppies, with a double allowance of imperfect feet. These, though somewhat connected with the rotifers, are considered to belong to the spider tribe.
Feeling that we must be merciful with the long¬ tailed words and explanations of classification, we reserve further matter of this kind for the oppor¬ tunities that must arise, and direct our attention to living forms by watching the Eugtence which our water-drop contains. We have before us a number of elegant spindle-shaped bodies, somewhat thicker in front than behind, and in what may be called the head there glitters a brilliant red speck, com¬ monly called an eye-spot , although, like the eyes of potatoes, it cannot see. Bound this eye-spot the tissues are clear, like glass; but the body of the creature is of a rich vegetable green, which shines
MARVELS OF POND-LIFE.
and. glistens as it catches the light. Some swim rapidly with a rollicking motion, while others twist themselves into all manner of shapes. Now, the once delicate spindle is oddly contorted, now it swells out in the middle, like a top, and now it rolls itself into a hall. The drawings will afford some idea of these protean changes, but they must
— a , motile; and b, resting condition of Euglenav
he seen before their harlequin character can he thoroughly appreciated. Some of the specimens exhibit delicate lines running lengthwise, and taking a spiral twist as the creature moves about; but in none can any mouth be discerned, and their antics, although energetic and comical, afford no certain indications of either purpose or will. What are they? animals or vegetables? or something betwixt and between?
The first impression of any casual observer would be to declare in favour of their animalitv; but before
V 1
this can be settled, comes the question, what is an animal, and how does it differ from a vegetable?
DISTINCTION BETWEEN PLANTS ANI) ANIMALS.
C} FL
<vV
and upon this the learned do by no means agree. One writer considers the presence of starch in any object a proof that it belongs to the dominions of
Flora, while another would decide the issue by as-
' %>
certaining whether it evolves oxygen and absorbs carbon, as most plants do, or whether it evolves carbon and absorbs oxygen, as decided animals do. Dr. Carpenter asserts that the distinction be¬ tween Protophyta and Protozoa, (first or simplest plants and animals,) “lies in the nature of their food, and the method of its introduction, for whilst the Protophyte obtains the materials of its nutrition from the air and moisture that surround it, and possesses the power of detaching oxygen, hydrogen, carbon, and nitrogen from their previous binary combinations, and of uniting them into ternary and quaternary organic compounds, (chlorophyll, starch, albumen, etc.,) the simplest Protozoa , in common with the highest members of the animal kingdom, seems utterly destitute of any such power, makes, so to speak, a stomach for itself in the substance of its body, into which it ingests the solid particles that constitute its food, and within which it subjects them to a regular process of di¬ gestion.”
Unfortunately it is very difficult to apply this simple theory to the dubious objects which lie on the border-land of the animal world, and no other
J26
MARVELS OF POND-LIFE.
theory that has been propounded appears to meet all cases. Some naturalists do not expect to find a broad line of demarkation between the two great divisions of living things, but others characterize such an idea as “unphilosophical,” in spite of which, however, we incline towards it.
Mr. Gosse, whose opinion is entitled to great respect, calls the Euglence ‘‘animals” in his “Evenings with the Microscope;” but from the aggregate of recorded observations it seems that they evolve ox- vgen. are coloured with the colouring matter of plants, reproduce their species in a manner analo¬ gous to plants, and have in some cases been clearly traced to the vegetable world. It is, however, possible that some Euglence forms may be animal and others vegetable, and while their place at nature’s table is being decided, they must be con¬ tent to be called Phytozoa , which, as we have before explained, is merely Zoophyte turned upside down.
Some authorities have thought their animality proved by the high degree of contractility which their tissues evince. This, however, cannot go for much, as all physiologists admit contractility to belong to the vegetable tissues of the sensitive plant, or “Venus’ Fly-trap,” and a little more or less cannot mark the boundary between two orders of being.
O
DESCRIPTION OF VORTICELLiE.
or
We shall have occasion again to notice the Pro - tophytes , and now pass to the Protozoa, of which we have a good illustration in the Vorticella already spoken of. In the group before us a number of elegant bells or vases stand at the end of long stalks, as shewn at the top of the frontispiece, while round the tops of the bells, the vibrations of a wreath of cilia produce little vortices or whirl¬ pools, and hence comes the family name. This current brings particles of all sorts to the mouth near the rim of the bells, and the creature seems not entirely destitute of power to choose or reject the morsels according to its taste. Every now and then the stalk of some specimen is suddenly twisted into a spiral, and contracted, so as to bring the bell almost to the ground. Then the stem gracefully elongates again, and the cilia repeat their lively game.
The general effect can be seen very well by a power of about sixty linear, but one of from one to two hundred is necessary to bring out the details, and a practised observer will use still more magnification with good effect. They should be examined by a moderately oblique light, or most of the cilia are apt to be rendered invisible, and also by dark ground illumination. This may be accomplished in a well-made microscope by turning the mirror quite out of the plane of the axis of
MARVELS OF FOND-LIFE.
the instrument, that is to say on one side of the space the body would occupy if it were prolonged. By this means, and by placing the lamp at an angle with the mirror, that must be learnt by experiment, all the light that reaches the eye has first passed through the object, and is refracted by it out of the line it was taking, which would have carried it entirely away. Or the object may be illuminated by an apparatus called a spotted lens , which is a small bull’s-eye placed under the stage, and having all the centre of its lace covered with a plaister of black silk. In this method the central or direct rays from the mirror are obstructed, but those which strike the edge of the bull’s-eye are bent towards the object, which they penetrate and illuminate if it is sufficiently transparent and re¬ fractive. Another mode of dark ground illumination is by employing an expensive instrument called a parabolic illuminator , which need not be described.
Different specimens and species of Vorticelloe vary in the length of their bells from one three or four- thousandth to one-hundred and twentieth of an inch, and when they are tolerably large, the dark ground illumination produces a beautiful effect. The bells shine with a pearly iridescent lustre, and their cilia flash with brilliant prismatic colours.
The Vorticellina belong to the upper division of the Protozoa— the ciliata, or ciliated animalcules, and
1 X T EST INAL C A N A L .
29
they have an intestinal canal with two orifices, one for the entrance, and the other for the exit of their food. Both these orifices are, to use the language of the u Micrographic Dictionary,” situated in the “same groove.” Here we have to notice two things,
O 0 7
Vorticella, with posterior circlet of cilia Vorticella in process of self-division. A in process of separation, iiOO linear. — new frontal wreath in fonnation in each Stein. °f the semi-lunar spaces.
both of which indicate some elevation in the scale of being. In the first place there is an intestinal tube , or distinct channel; while in the lowest ani¬ mals, such as the Amoeba or Protean animalcules
30
MARVELS OF FOND-LIFE.
there is no distinction of organs or parts. In the next place this tube has two orifices , one for re¬ ception, another for excretion ; while in animals like the Polyp, (to he described in our next chapter,) the digestive cavity has only one way in and out.
The bells or cups are not, as might be fancied from a casual inspection, open like wine-glasses at the top, but furnished with a retractile disk or cover,
Vorticella microstoma, shewing alimen¬ tary tube, ciliated mouth, and formation of a yemma at the base, 300 linear. — Stein.
Vorticella microstomo, the encysted animal protruding through a supposed rupture of the tunic.
on which the cilia are arranged. Their stalks are not simple stems, but are hollow tubes, which in the genus Vorticella are furnished with a muscular band, by whose agency the movements are principally made.
Some of the Vorticellids will be observed to leave their stalks, having developed cilia round their base, and may be seen to swim about in the enjoyment of
THE NUCLEUS OF THE VOKTICEI.LJE.
SI
individual life. They are also capable of becoming encysted , that is, of secreting a gelatinous cover, and likewise of assuming what Stein calls their Acineta forms, which are usually pear or trumpet¬ shaped bodies on short stalks, with stiff cilia or bristles springing from their heads. Stein thought that their Acineta forms never reproduced their own likeness, but always gave rise to Yorticellids of the original pattern. Other observers have, how¬ ever, seen young Acinetans developed by old ones, and therefore a part of Stein’s theory appears incor-
Encysted Vorticella, shewing the obliteration of special organs by the advancement of the process .—Pritchard.
rect. These changes are exhibited in the annexed cuts, which are copied from known authorities. By careful observation of the bodies of Yorticellids, a contractile vesicle may be observed, which appears to cause a movement of fluids, that is probably connected with respiration and the formation and repair of the substance of the animal. It uis placed against the upper part of the alimentary tube.”
Another piece of apparatus in this family, but not confined to it, is the so-called nucleus , which
MARVELS OF POND-LIFE.
m
in this case is of a horse-shoe shape and granular texture, and greater solidity than the surrounding parts. The functions of this organ form the subject of various conjectures, but it is generally held to be connected with the process of reproduction.
In common with many of the lower animals, the Yorticellids have three ways of multiplying their race. One by fission , or division of their bodies; another by buds, somewhat analogous to those of
Vorticella microstoma, in process of eneystment, 300 linear; in the last the inclosing tunic is plainly developed.— Stein.
plants; and another by reproductive germs. These processes will come again under our notice, and we shall leave the Yorticellids for the present by ob¬ serving that if they are fed with a very small quantity of indigo or carmine, the vacuoles or spaces, into which their nutriment passes, will be clearly observed. Ehrenberg thought in these and similar creatures that every vacuole was a distinct stomach, and that all the stomachs were connected by an intestinal canal ; hence his name PoJygostrica , or
WHEEL-BEARERS OR ROTIFERS. 33
many-stomached. In these views he has not been followed by later observers, and it is probable he was misled, partly by pushing the process of rea¬ soning from the analogies of higher animals much too far, and partly by the imperfection of the glasses he employed.
Rotifer vulgaris. — A, mouth, or gizzard; B, contractile ve sic\e.— Micrographic Dic¬ tionary.
N.B. — When the cilia and tail part are retracted, and the body shortened, the creature assumes an obtuse oval form.
Having thus briefly considered the Vorticellids, we must turn to the wheel-bearer, who belongs to a higher race than even the ciliated Protozoa. We left her crawling about with her snout or proboscis protruded, but now she has moored herself by her tail-foot, pulled in her nose, and put out two groups
D
MARVELS OF POND-LIFE.
34
of cilia, which look like revolving wheels, and a little below them is seen a gizzard in a state of active work. After a little while she swims away with her wheels going, and her tail, forked at the end, is found to be telescopic, or capable of being pulled in and out. As the cilia play, the neigh¬ bouring water is agitated, and multitudes of small objects are brought by the whirlpool within her ravenous maw. But the strangest thing of all is that inside her body is seen a young one; in this case a large and line infant, which, like “a chip of the old block,” imitates the parental mo¬ tions, thrusts forth its cilia, and works its gizzard.* In other genera the eggs are hatched externally, but this one is ovoviviparous, and carries its nursery inside.
A very slight investigation is sufficient to shew that in the wheel-bearer we have made a great advance towards a higher organization than we discovered in the preceding creatures. We witness what the learned call a “differentiation” of parts and tissues, and a “specialization” of organs. The head is plainly distinguishable from the body, the skin or integument is distinctly different from the internal tissues, behind the eyes we can detect a
* This was met with in the summer, but is described here to avoid repetition. I do not know whether the eggs are hatched in very cold weather.
TILE COMMON ROTIFER.
35
nervous ganglion or miniature brain, the gizzard is a complicated piece of vital mechanism, such as we have not met with before, and in various parts of the transparent inside we see organs to which par¬ ticular functions are assigned.
It was at one time thought that Rotifers were hermaphrodite —uniting both sexes in one body — but that idea is now generally abandoned, for in many species the males have been discovered, and the fair sex may lie gratified to hear that they are without doubt the inferior animals.” Their func¬ tion is simply to assist the female in producing young, and as this can be quickly accomplished, their lives are short, and they are not supplied with the gizzard and digestive apparatus, which their lady-loves pos¬ sess. Much discussion has taken place as to the rank which the Rotifers hold in the animal kingdom,
some naturalists thinking them relations of the crabs, and others believing them to belong to the family of the worms. Professor Huxley, who adopts the latter view, which has the most friends, groups the lower Annulosa together under the name of Annuloida , in which he includes Annelid es, or worms of various kinds, the Echninodermata , (or “spine skins,” among which are the star-fish and sea hedgehogs,) and some other families. He considers the Rotifers to be “the permanent forms of Echino- derm larvae.” This does not mean that they were
MARVELS OF POND-LIFE.
o/»
•)U
ever produced by Echinoderms, and had their de¬ velopment cheeked, but that they resemble them in organization, and illustrate a general law, observable in animated beings, namely, that the lower creatures are like the imperfect stages of higher animals, and that all things are formed according to general principles, and exhibit a uniformity of plan.
Mr. G osse adopts a different view, and while admitting a connection between the Rotifers and the worms, adduces important reasons for associating them with the insects.
Leaving zoologists to settle their position, we may remark that the Rotifers form a very numerous family, presenting very great diversities of structure, some of the most interesting of which we shall meet with in the course of our rambles; but they all possess a gizzard, which, though differing in com¬ plexity, is throughout formed upon the same principle, and that we must now explain.
We have called the masticatory apparatus of the Rotifers a gizzard ; but Mr. Gosse, who has done most to elucidate its structure, contends that it is a mouth ; and in some species it is frequently pro¬ truded, and used like the mouths of higher animals. Taking one of the most typical forms of this organ, and drawing our illustrations from Mr. Gosse’s ad¬ mirable paper in the “Transactions of the Royal Society,” we may describe it, when completely de-
STRUCTURE or THE GIZZARD.
O i
veloped, as consisting of tliree lobes, having a more or less rounded form. The eminent naturalist* we have named calls the whole organ, the mastax , and states that it is composed of dense muscular fibre. The tube which leads down to it, he desig¬ nates the “buccal (mouth) funnel,” and the tube that issues from it, and conveys the food to the digestive sac or stomach, he calls the oesophagus, in conformity with the nomenclature applied to creatures whose mouths are in their usual place. Inside the mouth-gizzard are placed two organs, which work like hammers, and which Mr. Gosse therefore names mallei. The hammers work against a sort of anvil, which is called incus , the Latin for that implement. Each hammer consists of two por¬ tions articulated by a hinge joint. The lower por¬ tion, the manubrium , or handle, gives motion to the upper portion, which from its shape is named the uncus , or hook. The unci are furnished with fin¬ ger-like processes or teeth, which vary in number. There are five or six in the best developed speci¬ mens. These hooks or teeth work against each other, and against the incus , or anvil, which consists of distinct articulated portions, of which the principal are two rami , or branches, jointed so that they can open and close like a pair of shears. These two rest upon a third portion, which is called the fulcrum. Some faint idea of the working of the toothed
88
MARVELS OF POND-LIFE.
hammers may be obtained by rubbing the knuckles of *both hands together, but the motion is more com¬ plicated, and the rami play their part in the tri- turition of the food. Mr. Gosse states that when an objectionable morsel has got as far as this mouth- gizzard, “it is thrown back by a peculiar scoop-like action of the unci, very curious to witness.” The appended diagram will help the reader to com¬ prehend this description, but no opportunity should
B
Gizzard of Notomata.
be lost for viewing this remarkable organ busy at work in the living animals.
The respiration of the Rotifers is supposed to be effected by the passage of water through vessels running round them, and called the “water vascular system,” and in addition to their eyes, which often disappear in adult specimens, the organ we described as standing out like a pig-tail, as our acquaintance crawled along, is thought to act as an antenna ,
ANTENNA OF ROTIFER
39
or feeler, and brings its possessor in further relation to the external world. It is also called the calcar , or spur, and is furnished with cilia or bristles at its extremity.
Sometimes the particles swallowed by the Common Rotifer are large enough for their course to be traced, but there is more frequently a great commotion and grinding of the gizzard, without* any appreciable cause, although doubtless something is taken in, and when the creature is tired, or has had enough, we see both head and tail retracted, and the body assumes a globular form. In another chapter, when viewing a Rhilodine, we shall see how in the family to which the Common Rotifer belongs, the gizzard departs from the perfect type.
CHAPTER, HI.
FEBRUARY.
VISIT TO HAMPSTEAD— SMALL PONDS— WATER-FLEAS— WATER- BEETLE— SNAILS— POLYPS— HYDRA VIRIDIS— THE DIPPING- TUBE— A GLASS CELL— THE HYDRA AND ITS PREY— CHYDORUS SPH^ERICUS AND CANTHOCAMPTUS, OR FRIENDS AND THEIR ESCAPES — COTHURNIA — POLYP BUDS — CATCHING POLYPS— MODE OF VIEWING THEM— STRUCTURE OF POLYPS— SARCODE —POLYPS STIMULATED BY LIGHT— ARE THEY CONSCIOUS?— TENTACLES AND POISON THREADS— PARAMECIUM— TRACHE- LIUS— MOTIONS OF ANIMACULES, WHETHER AUTOMATIC OR DIRECTED BY A WILL— THEIR RESTLESS CHARACTER.
CHAPTER III.
FEBRUARY.
It has been a bitterly cold night, and as the sun shines on a clear keen morning, and glistens in the hoar-frost which covers the trees, it might seem an unpropitious time for visiting the ponds, in search of microscopic prey. We will, however, try our luck, and take a brisk trot to the top of Hampstead Heath, where the air is still keener, and the ice more thick. Arriving at the highest point, London appears on one side enveloped in its usual great coat of smoke, through which St. Paul’s big dome, with a score or two of towers and steeples can be dimly made out; while looking towards Harrow-on-the-Hill, or Barnet, we see the advantage of country air in the sharpness with which distant objects cut the blue sky. We leave the large ponds for another time, and hunt out the little hollows among the furze and fern. One looks promising from the bright green vegetation to be discovered under the sheet of ice, which is almost firm enough to bear human weight.
44
MARVELS OF POND-LIFE.
Breaking a convenient hole we hook up some of the water-plants, and place them in a wide-mouthed vial, which we fill with water, and cursorily examine with a pocket-lens. Some water-fleas briskly skip¬ ping about, and a beautiful little beetle, with an elegant dotted pattern on his brown back, and a glistening film of air covering his belly, shew that we have not been unsuccessful, although we must wait till we get home to know the extent of our findings, among which, however, we can also discern the graceful spiral shell of a small water-snail, the Plan or bis.
Arriving at home the bottle was left undisturbed for some hours in a warm light place, and then on being examined several specimens of that beau¬ tiful polyp, the Hydra viridis , were seen attached to the glass, and spreading their delicate tentacles in search of prey. One of the polyps is carefully removed by the dipping-tithe , a small glass tube, open at both ends. The fore-finger is placed upon the top, and when the other end is brought over the object the finger is raised for an instant, and as the water rushes in the little hydra comes too, and is placed in a glass cell, about half an inch wide and one-tenth of an inch deep. These cells are obtained from the opticians, and cemented with var¬ nish or marine glue to an ordinary glass slide. After an object has been placed in one of them,
A GLASS CELL.
45
a little water is taken up in the clipping-tube, and
Hydra viridis with developed young one, and bud beginning to sprout.
the cell tilled until the fluid stands in a convex heap above its brim. We then select a round glass
MARVELS OF POND-LIFE.
46
cover, and press it gently on the walls of our cell. A few drops of superfluous water escape, and we have the cell quite full, and the cover held tight by force of the capillary attraction between the water and the glass.
The polyp deposited in one of these water cages is then transferred to the stage of the microscope, and its proceedings watched. At first it looks like a shapeless mass of apple-green jelly. Soon, how¬ ever, the tail end of the creature is fixed to the glass, the body elongates, and the tentacles (in this case eight) expand something after the manner of the leaves of a graceful palm.
By accident two small Water Fleas were imprisoned with the polyp, and one (a shrimp-like looking creature, carrying behind her a great bag of eggs,) came into contact with the tentacles, and seemed paralysed for a time. The hydra made no attempt to convey the captive to its mouth, but held it tight until another Water Flea, a round merry little fellow, ( Chydorus sphoericus J came to the rescue, and assisted Cantliocamptus to escape by tugging
action may not have been prompted by the intelligence which seemed to suggest it, but those who have kept tame soldier-crabs and prawns in an aquarium, will not be indisposed to attribute to the crustaceans more brains than they have usually credit for. It must, however, be con-
at her tail. This friendly
CANTHOCAMPTUS, CIIYDORUS, ETC.
47
fessed that tlie subsequent conduct of Mrs. Cantho- camptus did not indicate the possession of much prudence, for she learnt no lesson from experience, but repeatedly swam against her enemy’s tentacles.
A, Canthocamptus minutus; B, Chydorus sphcericus; C and D, Capsules and poison-thread ol polyp; E, Tricodina pedicuhts, side view and under view; F, Kerona polyporum. — Microg. Diet .
suffered many captures, and only escaped being devoured through the indifference, or want of ap¬ petite, which the polyp evinced.
48 MARVELS OF POND-LIFE.
On the body of the Canthocamptus were some small transparent vases or bottles, containing living objects, which sprang up and down. These were members of the Vorticella family, called Cothurnia and will be hereafter described.
Watching the hydra it was curious to note the changes of form which these creatures are able to assume. Now, the tentacles were short and thick, and the body scpiat; now the body was elongated,
Hydra viridis, in various shapes.
like the stem of a palm tree, and the tentacles hung gracefully from the top. From some of the polyps little round buds were growing, while other buds were already developed into miniature copies of the parent, and only attached by a slender stalk. In a few days many of these left the maternal side, fixed their own little tails to the glass, and commenced housekeeping on their own account.
Polyps may be obtained at all times of the year
CATCHING POLYPS.
4<>
by bringing home duckweed, conferva, aigl other water-plants from the ponds. Some hauls may be unsuccessful, but if one pond is not propitious others should be tried. The plants should be put in a capacious vessel of water, and placed in the light, where, if polyps be present, they will shew themselves within twenty-four hours, either attached to the sides of the glass, or hanging from the plants, or suspended head downwards from the upper film of the water. They are elegant objects, and may be kept without difficulty for some weeks. After being confined in a small quantity of water for purposes of examina¬ tion, they should be carefully replaced in the larger vessel, and may thus be used again and again without suffering any injury. A low power, — a three or two-inch glass — or a one-inch, reduced by employ¬ ing the erector, — is the most convenient for examining the whole creature, but higher powers are necessary to make out its minute structure. They should be viewed with direct and oblique light, as trans¬ parent and also as opaque objects. In the latter case the “Lieberkuhn,” or polished silver speculum, is convenient, and if the microscope is not furnished with Lister’s dark wells, a small piece of black paper may be stuck behind the object, by simply wetting it with the tongue.
Although the polyps are remarkable for the sim¬ plicity of their organization, they do not the less
E
MARVELS OF POND-LIFE.
•50
exhibit the wonderful nature of animal life. Their
f
bodies are composed of a uniform substance, called sarcode , in which is embedded a colouring matter resembling that in the leaves of plants; every part possesses irritability and contractility, and they are very sensitive to the stimulus of light. They may be cut and grafted like trees, and if turned inside out, the new inside digests and assimilates as well as the old. Whether any form of consciousness can belong to creatures which have no distinct nervous system is open to doubt, but it would seem probable from their movements that food and light afford them something like a pleasurable sensation in a very humble degree. If we were sufficiently acquainted with the secrets of molecular combination we might discover that the various functions of these simple organisms were discharged by different particles , although it is only in higher creatures that muscular particles are aggregated into muscles, or nerve par¬ ticles into nerves.
Having examined the general appearance and proceedings of the hydra, let us cut off a tentacle, or take a small specimen and gently crush it by pressing down the cover of the live box, and place the object so prepared under a power of about three hundred linear. If we then illuminate it with a moderate quantity of oblique light, we shall dis¬ cover round the edge of the tentacle a number of
TENTACLES AND POISON THREADS.
51
small cells or capsules, from some of which t a very slender wire or thread will he emitted.* These are the stinging organs of the polyp, and resemble those which Mr. Gosse has so ably elucidated in the sea anemones. Some writers have endeavoured to shew that they are not stinging organs at all, but so large an amount of evidence to the contrary is accumulated in Mr. Gosse’s “Actinologia Britannica,” that no reasonable doubt remains. The stinging capsules of the polyp are shewn in the annexed sketch, and also the way in which they are employed, for it fortunately happened that on exposing one of the hydras to pressure in the live box, a small worm (Anguilhda) escaped, which had been pierced with the minute weapons which are supposed to convey a poison into the wound. The authors of the “Micrographic Dictionary” think that the prongs of the forks, which will be seen to point upwards in the sketch, *j* are springs, and occupy a reversed position in the capsule cells, and that their func¬ tion is to throw out the threads. However this may be, the polyps, and similarly endowed creatures, have the power of darting out their poison-threads with considerable force, and Mr. Gosse found that the anemone was able to pierce a thick piece of human skin.
The same excellent observer attributes the emis- * See page 47, C and D.
f See page 52.
MARVELS OF P0NI)-1,1FE.
sion of the anemone poison threads, which he considers hollow, to the injection of a fluid. Jn their quiescent
Anguillula pierced by stinging organs of the Hydra viridis.
state, he thinks they are drawn in, like the finger of a glove, and are forced out as the liquid enters
their slender tubes. Possibly the polyp stinging organs may have the same structure.
Notwithstanding their dangerous weapons, polyps are often infested with a parasite, the Trichodina pedicidus , as shewn in Fig. E, page 47, and it must happen that either this visitation is not disagreeable, or that the Trichodina is not influenced by the poison.
As the plants in the bottles decayed, some of the animalcules died off and others appeared. In one bottle, containing decaying chara, Paramecia abounded. The Paramecia , of which there are various species, have always been favourite objects with microscopists. The Germans call them “slipper animalcules, ” and they vary in size from 1—96 ' ^ to 1-1150". They are flat rounded-oblong creatures, with a distinct integument or skin, “through which numerous vibratile cilia pass in regular rowsd’f They are furnished with a distinct mouth, and adult specimens exhibit star-shaped contractile vesicles in great perfection.
The swarm of specimens before us belong to one species, Paramecium aurelia , the Chrysalis animal¬ cule. , and they crowd every portion of the little water-drop we have taken up, and examined with
# The usual mode of giving dimensions is by fractions thus expressed, — 1-96" means one-ninety-sixth of an inch.
f Micrographic Dictionary.
54
MARVELS OF POND-LIFE.
a power of about one hundred linear. When they are sufficiently cpiiet a power of about four hundred may be used with advantage, and Pritchard recom¬ mends adding a little indigo and carmine to the water, in order to see the cilia more clearly, or rather to render their action more plain. The cilia are disposed lengthwise, and Ehrenberg counted in some rows sixty or seventy of them, making an aggregate of three thousand six hundred and forty organs of motion in one small animated speck. This number seems large, but although we have never performed the feat of counting them, we should
Paramecium aurelia.
A dried specimen shewing the vesicles.— Pritchard.
have expected it to prove much greater. Unlike most animalcules they are susceptible of being pre¬ served by drying upon glass, and we subjoin a figure from Pritchard, of one thus treated, in which the star-shaped vesicles are clearly seen. These curious organs communicate with other vessels, and as wre have previously stated, are probably connected with
TRACH ELI US.
55
respiration and circulation, although some naturalists entertain a different opinion.
The genus Paramecium is now confined to those creatures which exhibit rows of longitudinal cilia of uniform length, which are destitute of hooks, styles, or other organs of motion other than cilia, which have a lateral mouth, and no eye-spots. Their mode of increase is by division, which may be easily observed.
Another of the treasures from the pond was a species of Trachelius , or long-necked ciliated ani¬ malcule, which kept darting in and out of a slimy den, attached to the leaf of a water-plant. The body was stout and fish-shaped, the tail blunt, and the neck furnished with long conspicuous cilia, which enabled the advancing and retreating move¬ ments to be made with great rapidity. The motions of this creature exhibit more appearance of purpose and design than is common with animalcules, but in proportion as these observations are prolonged, the student will be impressed with the difficulty of assuming that anything like a reasoning faculty and volition, is proved by movements that bear some resemblance to those of higher animals, whose cere¬ bral capacities are beyond a doubt. It is, however, almost impossible to witness motions which are neither constant nor periodic, without fancying them to be dictated by some sort of intelligence. We
56
MARVELS OF POND-LIFE.
must, nevertheless, be cautious, lest we allow our¬ selves to be deceived by reasoning so seductive, as the vital operations of the lowest organisms may be merely illustrations of blind obedience to stimuli, in which category we must reckon food, and until we arrive at forms of being which clearly possess a ganglionic system, we have no certainty that a real will exists, even of the simplest kind; and perhaps we must go still higher before we ought to believe in its presence.
Ehrenberg was much struck with the restless character of many infusoria — whether he looked at them by day or by night, they were never still. In fact their motions are like the involuntary actions which take place in the human frame; and if at¬ tached to their bodies we observe cilia that never sleep, the living membrane of some of our own organs, the nose, for example, is similarly ciliated, and keeps up a perpetual though unconscious work.
CHAPTER IV.
MARCH.
PARAMECIA— EFFECTS OF SUNLIGHT— PTERODINA PATINA- CURIOUS TAIL— USE OF A COM PRESSORIUM— INTERNAL STRUC¬ TURE OF PTERODINA— METOPIDIA— TRICIIOD1NA PEDICULUS — COTHURNIA— SALPINA-ITS THREE-SIDED BOX— PROTRUSION OF ITS GIZZARD MOUTH.
CHAPTER IV.
MARCH.
The Paramecin , noticed in the last chapter, have increased and multiplied their kind without any fear, lest the due adjustment between population and food should fail to be preserved. A small drop of the scum from the surface of the water in their bottle is an astounding sight. They move hither and thither in countless numbers, seldom jostling, although as thick as herrings in a tub, and in many portions of the field the process of self-fissure, or multipli¬ cation by division, is going on without any symptoms of discomfort on the part of the parent creature. This is an interesting sight, but we will not linger over it, for the sun is shining, and there is enough warmth in the air to make it probable that the ponds will be more prolific than in the cold winter months. Sunshine is a great thing for the micro¬ scopic hunter; it brings swarms of creatures to the surface, and the Rotifers are especially fond of its genial beams. Even if we imitate it by a bright lamp, we shall attract crowds of live dancing specks
<>0 MARVELS OF POND-LIFE.
to the illuminated side of a bottle, and may thus easily effect their capture by the dipping-tube.
This year the March sunshine was not lost, for on the 3rd. of that month I obtained a bottle full of conferva from a pond about a mile from my house, and lying at the foot of the ITighgate hills. Water-fleas were immediately discovered in abundance, together with some minute worms, and a ferocious- looking larva covered with scales; but what attracted most attention was a Rotifer, like a transparent
animated soup-plate, from near the middle of which depended a tail, which swayed from side to side, as the creature swam along. The head exhibited two little red eyes; two tufts of cilia rowed the living disk through the water, and the gizzard worked with a rapid snapping motion, that left no doubt the ciliary whirlpools had brought home no slender stores of invisible food. Sometimes the end of the tail acted as a sucker, and fixed the animal tightly to
PTERODINA PATINA.
61
the glass, when the wheels were protruded, and the body swayed to and fro. Then the sucker action ceased, and as the creature swam away, a tuft of cilia was thrust out from the extremity of the tail. A power of one hundred linear was sufficient to enable the general nature of this beautiful object to be observed, but to bring out the details, much greater amplification was required, and this would
Pterodina patina— gizzard.
«
be useless if the little fidget could not be kept
still.
The size of the creature, whose name we may as well mention was Pterodina patina , rendered this practicable, but required some care. The longest diameter of the body, which was not quite round, was about 1-120", so that it was visible to the naked eye, and as a good many were swimming together, one could be captured without much difficulty, and
6,2 marvels of pond-life.
transferred with a very small drop of water to the live box. Then the cover had to be put on so as to squeeze the animal just enough to keep it still without doing it any damage, or completely stopping its motions. This was a troublesome task, and often a little over-pressure prevented its success.
Some observers always use in these cases an in¬ strument called a compressorium , by which the amount of pressure is regulated by a lever or a fine screw; but whether the student posseses one or not,
rterodina patina— tail-foot.
he should learn to accomplish the same result by
9
dexterously manipulating a well-made live box. We will suppose the Pterodina successfully caged, and a power of about one hundred and fifty linear brought to bear upon her, for our specimen is of the “female persuasion.” This will suffice to demonstrate -the disposition and relation of the several parts, after which one of from four hundred to five hundred linear may be used with great advantage, though in this case the illumination must be carefully adjusted, and
INTERNAL STRUCTURE OE PTERODINA.
63
its intensity and obliquity frequently changed, until the best effect is obtained.
We find, on thus viewing the Pterodina, that it is a complex, highly-organized creature, having its body protected by a carapace , like the shell of a tortoise, but as flexible as a sheet of white gelatine paper, which it resembles in appearance. Round the margin of this carapace are a number of little bosses or dots, which vary in different individuals. The cilia are not disposed, as at first appeared, in two separate and distinct disks, but are continuous, as in the annexed sketch. Down each side are two long muscular bands, distinctly striated, and when they contract, the ciliary apparatus is drawn in. As this contraction takes place, two apparently elastic bands, to which the ciliary lobes are attached, are bent downwards, till they look like the C springs behind a gentleman’s carriage; and they regain their former position of slight curvature, when the cilia are again thrust out.
The gizzard is three-lobed, and curiously grasped by forked expansions of the handles of the hammers. The tail, or tail-foot, can be withdrawn or thrust out at the will of the creature; and when in a good position for observation, a slight additional pressure will keep it so for examination. Delicate muscular longitudinal bands, forked towards the end of their course, supply the means of performing some of its
MARTELS OF POND-LIFE.
(>4
motions, and one, or perhaps two, spiral threads extend through the upper half of its length, and either act as muscles, or as elastic springs for its extension. The intestines and other viscera are clearly exhibited, and a strong ciliary action con¬ ducts the food to the gizzard •mouth.
To return to the tail. One spiral fibre is easily discovered ; but I have often, and at an interval of months, seen the appearance of two, and am in some doubt whether this was a deception, arising from the compression employed, or was a genuine indication.
Where this Rotifer occurs I have usually found it plentiful, but unfortunately could obtain no con¬ stant supplies after I had determined to make a special study of the remarkable tail, which is much more complicated than I have described. The Pterodina lived for some time in captivity, and for a week or two I could obtain them from my glass tank. They were likewise to be found for some weeks in the same part of the pond, but not all over it, until one day not a single specimen could be discovered, notwithstanding a persevering search, nor was I afterwards able to get any from that pond during the remainder of the year.
%J
Several other Rotifers, with and without carapaces, were among the same mass of confer vie, among them
M ET 0 P I ] ) 1 A A CUMIN A I' A .
65
a Metopidia , with a firm shell, a forked jointed tail, and a projection in front which worked like a pick-axe among the decaying weed. There were likewise specimens of the long-necked animalcules, (Traehelii, ) groups of Vorticella, some specimens
A, Metopidia acuminata, as drawn by Mr. Gosse. B, Specimen as seen nr^d described in text; c, Mouth or gizzard.
of Yolvox, and a small Trichodina pediculus , which, when magnified two hundred and sixty linear, was about the size of a sixpence, and equally round. The edge was beautifully fringed with a circle of cilia; in an inner circle was a row of locomotive organs, and the centre exhibited vacuoles constantly opening and shutting. This creature, as before explained, is often found, as a parasite upon the
MARVELS OF POND-LIFE.
66
polyps. On one occasion a glimpse was caught of a Rotifer similar in shape to the common wheel animalcule, but with a yellow inside. Pos¬ sibly it was the object so beautifully delineated by Mr. Gosse, in his “Tenby,” and described as the “Yellow Philodine,” but this must remain in doubt, as it managed to escape before it could be secured.
Trichodina pediculus.
By the 18th. of the month the Vorticellids were much more plentiful, and their changes easily watched ; many left their stalks while under the microscope, after which some rushed about like animated and demented hats, others twirled round like tee-to-tums, while others took a rest before commencing their wild career. But the common Yorticellae were not the only or the most interesting representations of their charming family, for upon some threads of conferva were descried several elegant crystal vases standing upon short foot¬ stalks, and containing little creatures that jumped up and down like “Jack in the box.” These were so minute, that a power of four hundred and
COTHURNI A. 67
Cotburnia imberbis— (“Micrograph. Diet.”) B and C, the specimens described in text. The figures give the linear magnification.
68
MARVELS OF POND-LIFE.
thirty linear was advantageously brought to bear upon them. When elongated their bodies were somewhat pear-shaped, but more slender, and variegated with vacuoles and particles of food. The mouths resembled those of Vorticellse, and put forth circles of vibrating cilia. They were easily alarmed, when the cilia were retracted, and down they sank to the bottom of their vases, quickly to rise again. In one bottle there were two living in friendly juxtaposition. This was not a case of matrimonial felicity, nor of Siamese twins, but of fission , or reproduction by division. The original inhabitant of the tube finding himself too fat, or impelled by causes we do not under¬ stand, quietly divided himself in two, and as the house was big enough, no enlargement was required. How many stout puffy gentlemen must envy this process; how convenient to have two thin lively specimens of humanity made out of one too obese for locomotion. Man is, however, sometimes the victim of his superior organization, and no process of “fission” can make the lusty lean.
The bottles in which these creatures live, in happy ignorance that they are called by so crack- jaw a name as Cothurnia imberbis , were described as Carapaces by Ehrenberg, but they bear no re¬ semblance to the shell of a turtle or a crab. Thev are thrown off by the animals who preserve no
MOTIONS OF ANIMALCULES.
69
other connection with them than the attachment at the bottom. The Cotliurnia are separated by some writers from the Vorticellids, but while that family is permitted to contain the Stentors , one of which is often found in a gelatinous tube, the Cotliurnia and their allies may remain in it without disadvantage.
Towards the end of the month a great number of black pear-shaped bodies, visible to the naked eye, were conspicuous in some water from the Kentish Town ponds. Upon examination they were found to be filled with granules that were red by reflected, and purple by transmitted light. Each one had a spiral wreath of cilia, with a mouth situated like those of the Stentors, here¬ after to be described, but none of them became stationary, and in a few days they all disappeared. In the same water were specimens of that singular Rotifer, the Salpina , about 1-150" long, and furnished with a lorica , or carapace, resembling a three-sided glass box, closed below, and slightly open along the back. At the top of this box were four, and at the bottom three, points or horns, and the creature had one eye and a forked tail. Keeping him company was another little -Rotifer, named after its appearance, Monocerca rattus , the ‘One-tailed Rat.' This little animal had green matter in its stomach, which was in constant commotion. 1
70
MARVELS OF POND-LIFE.
ought to have observed that the Salpina repeatedly thrust out its gizzard, and used it as an external mouth. In the annexed sketch the Salpina is seen in a position that displays the dorsal open¬ ing of the carapace. Its three-cornered shape is only shewn by a side view.
Here we close a brief account of what March winds brought in their train. The next chapter will shew the good fortune that attended April showers.
Salpina "redunca.
CHAPTER Y
APRIL.
THE BEAUTIFUL FLOSCULE— MODE OF SEEKING FOR TUBICOLOR ROTIFERS — MODE OF ILLUMINATING THE FLOSCULE— DIFFI¬ CULTY OF SEEING THE TRANSPARENT TUBE— PROTRUSION OF LONG HAIRS— LOBES— GIZZARD-HAIRY LOBES OF FLOS¬ CULE NOT ROTATORY ORGANS— GLASS TROUGHS -TIIEIR CON¬ STRUCTION AND USE— MOVEMENT OF GLOBULES IN LOBES OF FLOSCULE— CHiETONOTUS LARUS— ITS MODE OF SWIMMING— COLEPS HIRTUS— DEVOURER OF DEAD ENTOMOSTRACA— DEAD ROTIFER AND VIBRIONES— THEORIES OF FERMENTATION AND PUTREFACTION— EUPLOTES AND STY LONICH I A— FECUNDITY OF STYLONICHIA.
CHAPTER V.
APRIL.
Few living creatures deserve so well the appel¬ lation of “beautiful” as the Floscularia ornata , or Beautiful Floscule, although to contemplate a motionless and uncoloured portrait, one would imagine that it exhibited no graces of either colour or form. Mr. Gosse has, however, done it justice, and the drawing in his “Tenby” is executed with that rare combination of scientific accuracy and artistic skill, for which the productions of his pencil are renowned.
Probably the sketches in several works of authority, representing the long cilia as short bristles, are merely copies from old drawings, from objects imperfectly seen under indifferent micro¬ scopes, and before the refinements of illumination were understood. Be this as it may, any reader will be fortunate if on an April, or any other morning, he or she effects the capture of one of these exquisite objects, although the first impression
74
MARVELS OF POND-LIFE.
may not equal previous expectations, as the delicacy of the organism is not disclosed by a mode of using the light which answers well enough for the common infusoria.
When the Floscules, or other tubicolor Rotifers are specially sought for, the best way is to pro¬ ceed to a pond where slender-leaved water-plants grow, and to examine a few branches at a time in a phial of water with a pocket-lens. They are all large enough to be discerned, if present, in this manner, and as soon as one is found, others may be expected, either in the same or in adjacent parts of the pond, for they are gregarious in their habits. With many, however, the first finding of a Floscule will be an accident, as was the case last April, when a small piece of myrio- phyllum was placed in the live-box, and looked over to see what it might contain. The first glimpse revealed an egg-shaped object, of a brownish tint, stretching itself upon a stalk, and shewing some symptoms of hairs or cilia at its head. This was enough to indicate the nature of the creature, and to shew the necessity for a careful management of the light, which being adjusted obliquely, gave quite a new character to the scene. The dirty brown hue disappeared, and was replaced by brilliant colours; while the hairs, instead of appearing few and short, were found to be extremely numerous,
THE BEAUTIFUL FLOSCULE.
75
very long, and glistening like delicate threads of spun glass.
Knowing that the Floscules live in transparent gelatinous tubes, such an object was carefully looked for, but in this instance, as is not uncommon, it was perfectly free from extraneous matter, and pos¬ sessed nearly the same refractive power as the water, so that displaying it to advantage required some little trouble in the way of careful focusing, and many experiments as to the best angle at which the mirror should be turned to direct the light. When all was accomplished, it was seen that the Floscule had her abode in a clear transpa¬ rent cylinder, like a thin confectioner’s jar, which she did not touch except at the bottom, to which her foot was attached. Lying beside her in the bottle were three large eggs, and the slightest shock given to the table, induced her to draw back in evident alarm. Immediately afterwards she slowly protruded a dense bunch of the fine long hairs, which quivered in the light, and shone with a delicate bluish green lustre, here and there varied by opaline tints.
The hairs were thrust out in a mass, somewhat after the mode in which the old-fashioned telescope hearth-brooms were made to put forth their bristles. As soon as they were completely everted, together with the upper portion of the Floscule, six lobes
MARVELS OF POND-LIFE.
76
gradually separated, causing the hairs to fall on all sides in a graceful shower, and when the process was complete, they remained perfectly mo¬ tionless, in six hollow fan -shaped tufts, one being attached to each lobe. Some internal ciliary action, quite distinct from the hairs, and which has never been precisely understood, caused gentle currents to tiow towards the mouth in the middle of the lobes, and from the motion of the gizzard, imperfectly seen through the integument, and from the rapid tilling of the stomach with particles of all hues, it was plain that captivity had not destroyed the Floscule’s appetite, and that the drop of water in the live box contained a good supply of food.
Sometimes the particles swallowed were too small to be discerned, although their aggregate effect was visible; but often a monad or larger object was ingulfed, but without any ciliary action being visible to account for the journey they were evidently compelled to perform. The long hairs took no part whatever in the foraging process, and as they do not either provide victuals or minister to locomotion, they are clearly not, as was supposed by early observers, representatives of the “wheels,” which the ordinary Rotifers present. Neither can the cylindrical jar or bottle be justly deemed to occupy the position of the lorica, or carapace which we have before described. The general
77
ABSENCE OF “WHEELS.”
structure of the creature and the nature of its gizzard, distinctly marked it out as a member of the family we call “ Rotifers,” but the absence of anything like “wheels” proves that those organs are not essential characteristics of this class.
Noticeable currents are not always produced when the mouth of this Floscule is fully expanded. On one occasion, one having five lobes was discovered standing at such an angle in a glass trough that the aperture could be looked down into. The position rendered it impossible to use a higher power than about two hundred linear, but with this, and the employment of carmine, nothing like a vortex was seen during a whole evening, although a less power was sufficient to shew the ciliary whirlpools made by small specimens of Epistylis and Vaginicolci , which were in the same vessel. The density of the integument was unfavourable to viewing the action of the gizzard, but it could be indistinctly perceived. The contractions and subsequent expan¬ sions of the cup, formed by the upper part of the creature, may be one way in which its food is drawn in, but there is no doubt it can produce currents when it thinks proper. Sometimes ani¬ malcules in the vicinity of Floscules whirl about as if under tbe influence of such currents. Some may be seen to enter the space between the lobes, swim about inside, and then get out again, while
7 C O /
78
MARVELS OF POND-LIFE.
every now and then one will be sucked in too far for retreat.
Above the gizzard in the Horned Floscule,^ I have seen an appearance as if a membrane or curtain was waving to and fro, while another was kept in a fixed perpendicular position. Mr. Gosse, speaking of this genus, observes “that the whole of the upper part of the body is lined with a sen¬ sitive, contractile, partially opaque membrane, which a little below the disk recedes from the walls of the body, and forms a diaphragm, with a highly contractile and versatile central orifice. At some distance lower down another diaphragm occurs, and the ample chamber thus enclosed forms a kind of crop, or receptacle for the captured prey.”
“From the ventral side of the ample crop that precedes the stomach, there springs in F. ornata a perpendicular membrane or veil, partly extending across the cavity. This is free, except at the
# The Horned Floscules (F. cornuta) which I have found, and which bred in a glass jar, were not so large as those described by Mr. Dobie, as quoted in “Pritchard’s Infusoria.” Mr. D.’s specimens were 1-40" when extended; mine about half that size, five-lobed, and with a long slender proboscis, standing in a wavy line outside one lobe. Mr. Dobie also describes an F. campa- nulaia, with five flattened lobes. The “Micrographic Dictionary” pronounces these two species “doubtfully distinct.” I have three or four times met with a variety of F. ornata, in which one lobe was much enlarged and flattened, but they had no probos¬ cis. In what I take for F. cornuta, the horn or proboscis has sometimes been a conspicuous object, and at others so fine and transparent as to be only visible in certain lights.
MOVEMENT OF GLOBULES IN LOBES OF FLOSCULE. T9
vertical edge, by which it is attached to the side of the chamber, and being ample and of great delicacy, it continually boats and waves from side to side. At the bottom of this veil , but on the dorsal side, are placed the jaws, consisting of a pair of curved, unjointed, but free mallei , with a membranous process beneath each.”
The Beautiful Floscule could always be made to repeat the process of retreating into her den, and coming out again to spread her elegant plumes before our eyes, by giving the table a smart knock, and her colours and structure were well exhibited by the dark-ground illumination, which has been ex¬ plained in a previous page.
An object like this should be watched at in¬ tervals for hours and even days, especially if the eggs are nearly ready to give up their infantile contents. This was the case with the specimen described, and after a few hours a young Floscule escaped, looking very much like a clumsy little grub. After a few awkward wriggles the new-born baby became more quiet, and on looking at it again at the expiration of seventeen hours, it had developed into the shape of a miniature plum-pudding, with hve or six tiny lobes expanding their tufts of slender hair. Unfortunately its further proceedings were not seen, or it would have been interesting to note the growth of the foot, and the formation of the
80
MARVELS OF POND-LIFE.
gelatinous tube, which is probably thrown off in rings.
To view the details of the structure of a Floscule, it must be placed in a live-box or compressorium, and if specimens are scarce, they should not be allowed to remain in the limited quantity of water those contrivances hold, after the observations are concluded, but should be carefully removed, and placed in a little vial, such as homeopathists use for their medicine. By such means an individual may be kept alive for many days. It is also interesting to place a little branch of the plant occupied by Floscules or similar crea¬ tures, in a glass trough, where they may be made quite at borne, and their proceedings agreeably watched by a onednch or two-thirds power. These troughs, which can be obtained of the optician, should be of plate glass, about three inches long, nearly the same height, and about half an inch wide. If narrower, or much taller, they will not stand, which is a great inconvenience. The pieces of glass are stuck together with marine glue, and a very simple contrivance enables the plants or other objects to be pressed near the front, and thus brought into better view. A strip of glass, rather narrower than the width of the trough, is dropped into it, and allowed to fall to the bottom. Then a piece of glass rather shorter than the trough,
LOBES OF FLOSCULE.
si
and rather higher than its front side, is placed so as to slope from the front of the bottom towards the back at the top. The piece of glass first dropped in keeps it in the right position, and the trough is thus made into a Y-shaped vessel, wide at the top and gradually narrowing. Any object then placed in it will fall till it fits some part of the Y, where it will remain for observation. A small weda'e of cork enables the moveable piece of glass to be thrown forwards, until it assumes any angle, or is brought parallel to the front of the trough.
A power of five or six hundred diameters generally enables a movement of small globules to be seen at the extremity of the lobes of the Floscule, and the gizzard may be made plain by dissolving the rest of the creature in a drop of solution of caustic potash. It also becomes more visible as the supply of food falls short. Mr. Gosse describes the bodv as “lined with a yellowish vascular membrane,” and young specimens exhibit two red eyes, which may or may not be found in adults. When these eyes of Rotifers are not readily conspicuous, they must be sought for by opaque illumination, or by the dark-ground method which, especially with the parabola, is successful in bringing them out.
Naturalists, and possibly the specimens also, do not always agree in the number of lobes assigned to the “Beautiful Floscule, ” and although it is easy
G
MARVELS OF POND-LIFE.
82
enough to count them in some positions, the observer may have to exercise a good deal of patience before he is certain whether they are five or six. For a long evening only live could be discerned in the specimen now described, but the next night six were apparent without difficulty or doubt. The hairs also will not appear anything like their true length or number, unless the object glass is good, and great care is taken not to obscure them by a blaze of ill-directed light.
After the Floscules had been sufficientlv admired and put aside, for observations to be repeated on future occasions, a Rotifer attracted attention by his merry-andrew pranks, throwing himself in all direc¬ tions by means of two long and extremely mobile toes attached to his tail-foot. Then came a creature swimming like an otter, thrusting his head about on all sides, and looking much more intelligent than most of his compeers of the pond. Looked at ver¬ tically, he was somewhat slipper-shaped, the rounded heel forming his head, then narrowing to a waist, and expanding towards the other end, which pro¬ jected in a fork. All round him were long cilia, which were conspicuous near the head, and a fine line indicated the passage from his mouth to the stomach, which seemed full of granular matter. Presently he took to crawling, or rather running, over a thread of conferva, and then his back was
CHJETONOTUS LARUS.
8.3
elegantly arched, and his cilia stood erect like the quills of a porcupine. This was the Chcetonotus larus.
In Pritchard’s “Infusoria,” the views of those writers are followed who rank this animal amongst the Rotifers, and place it in the family Icthidina. To help out this theory, the cilia upon the ventral surface are imagined to form a “hand-like rotary organ;” but in truth they bear no resemblance
Chsetonotus larus, (swimming-.)
whatever to the so-called wheels of the ordinary Rotifers, nor is there anything like the gizzard which true Rotifers present. Ehrenberg treated it as a Rotifer, and Dujardin placed it among the Infusoria, in a particular class, comprehending sym¬ metrical organisms. The “Microscopic Dictionary” remarks that its “structure requires further inves¬ tigation,” and while the learned decide all the intricate questions of its zoological rank, the ordinary
84
MARVELS OF POND-LIFE.
observer will be pleased to watch its singular aspect and lively motions. Its size, according to the uMi- crographic Dictionary,” varies from 1-710" to 1— 220", and while its general proceedings may be watched with an inch or two-thirds object glass, and the second eye-piece, a power of five hundred linear (obtained by a quarter or a fifth) is required to make out the details of its structure. If placed in a live-box with threads of conferva, and a little decayed vegetation, it may be observed to grope
520
Clisetonotus larus, (crawling.)
about among them, and shake them like a dog.
We have said that water-fleas were among the inhabitants of a bottle filled at the pond, and as they go the way of all flesh, it is common to find some odd-looking animalcules ready to devour their mortal remains. These are creatures shaped like beer-barrels, upon short legs, and which swim with a tubby rolling gait. Looking at one of these little tubs lengthwise, a number of lines are seen, as though the edge of each stave projected a little
DEAD ROTIFER AND VIBRI0N ES.
85
above the general level, and transverse markings are also apparent, which may be compared to hoops. This is the Coleps hirtus , which differs from the usual type of Infusoria, by being symmetrical, that is, divisible into two ecpial and similar halves. The dimensions of this species vary from 1-570 to 1-430, and its colour varies from white to brown. It has been observed to increase by transverse self-
Coleps hirtus.
division, and has two orifices, one at each end, for receiving food and ejecting the remains. It often requires some little trouble to get a good view of the cilia, which are arranged in transverse and longitudinal rows. A power of one hundred and fifty linear is convenient for viewing it in motion, but when quiet under pressure, one of five or six hundred may be used with advantage.
Among the rubbish at the bottom of the bottle, in which the coleps was found, was a minute dead
86
MARVELS OF FOND-LIFE.
Rotifer, the flesh of which was fast disappearing, hut upon being examined with a poAver of nine hundred and sixty diameters, it was observed to swarm wi th extremely minute vibriones , the largest only appearing under that immense magnification like chains of bluish green globules, not bigger than the heads of minikin pins, Avhile the smallest Avere knoAvn by a worm-like wriggling, although their structure could not be defined. These vibriones are probably members of the vegetable world, and they always appear when animal matter undergoes pu¬ trefaction.
M. Pasteur has recently brought forward elaborate experiments to sheAv that the development of the yeast plant is an act correlative to alcoholic fermen¬ tation, and in like manner the groAvth of vibriones may stand in correlation to putrefactive decompo¬ sition.
Ehrenberg considered them animals, and fancied he detected in them a plurality of stomachs; but the vegetable theory is the more probable, at any rate of the species under our notice, Avhich is often seen, though not always so minute.
At this time two interesting animalcules were very plentiful — the Euplotes patella , and Stylonichia , both remarkable as exhibiting an advance in organ¬ ization, which approximates them to the higher animals. In addition to cilia they possess styles ,
ETJPLOTES AND STYLONTCHTA.
ST
which take the place of the limbs of more elaborately- constructed creatures, and give a variety to their means of locomotion. The Ewplotes is furnished with an oval carapace covering the upper surface, which in different individuals, and probably at different ages, exhibits slightly varied markings round its margin, which in the specimen drawn below con¬ sisted of dots. They can run, climb, or swim, and exemplify a singular habit which several of the
A, Euplotes (patella;) B, side view of ditto; C, Stylonichia.
infusoria possess, that of moving for a little time in one direction, and then suddenly, and without any apparent cause, reversing it. If the reader is fond of learned appellations, he can call this diastrophy , but we do not know that he will be any the wiser for it.
The Stylonichia are oval animalcules, surrounded by cilia, and having moreover a collection of styles, both straight and curved, the latter called nneini ,
or little hooks. They swim steadily on, and then dart back, blit not so far as they have advanced, and may be seen to keep up this fidgetty motion by the hour together. Pritchard tells us Ehrenberg found that a single animalcule lived nine days; during the first twenty-four hours it was developed by transverse self-division into three animals; these in twenty-four hours formed two each in the same manner, so that by self-division only, (without ova,) these animalcules increased three or four-fold in twenty-four hours, and may thus produce a million from a single animalcule in ten days. Such are the amazing powers of reproduction conferred upon these humble creatures, powers which are fully employed when the surrounding circumstances are favourable, and which, in the aggregate, change the condition of large masses of matter, and bring within the circle of life millions upon millions of particles every minute of the day.
CHAPTER VI.
MAY.
F LOSC UL Alii A CORNUTA— EUCHLANIS TRIQUETRA— MELICER- TA RINGENS— ITS POWERS AS BRICK-MAKER, ARCHITECT, AND MASON— MODE OF VIEWING THE MELICERTA— USE OF GLASS CELL— HABITS OF MELICERTA— CURIOUS ATTITUDES— LEAVE THEIR TUBES AT DEATH— CARCHESIUM — EPISTYLIS — THEIR ELEGANT TREE FORMS -A PARASITIC EPISTYLIS LIKE THE “OLD MAN OF THE SEA”— HALTERIA AND ITS LEAPS— ASPIDISCA LYNCEUS.
00
Melicerta rmgens.
CHAPTER VI.
MAY.
May, the first of summer months, and of old famous for fioral games, which found their latest patrons in the chimney-sweeps of London, is a good time for the microscopist among the ponds, for the increase of warmth and heat favours both animal and vegetable life, and so we found as we carried home some tops of myriophyllum, and soon discov¬ ered a colony of tubicolor rotifers among the tiny branches. They proved to be Floscules, generally resembling the F. ornata , described in a previous page, but having a long slender proboscis hanging like a loose ringlet down one side. The cilia or hairs were not so long as in the Beautiful Flos¬ cules we had before obtained, nor was their manner of opening so elegant; but they were, nevertheless, objects of great interest, and were probably speci¬ mens of the Floscularia cornuta. A swimming rotifer in a carapace somewhat fiddle-shaped, with one eye in its forehead, and a two-pronged tail
92
MARVELS OF POND-LIFE.
sticking out behind, (the Euchlanis triquetra ,) also served to occupy attention ; but a further search among the myriophyllum revealed more treasures of the tube-dwelling kind. These were specimens of that highly curious Rotifer, the Melicerta ringens , who, not content with dwelling, like the Floscules, in a gelatinous bottle, is at once brick-maker, mason, and architect, and fabricates as pretty a tower as it is easy to conceive. The creature itself stands upon a retractile foot-stalk, and thrusts out above its battlements a large head, with four leaf-like expansions surrounded by cilia. Between the lower lobes, or leaves, the gizzard is seen grinding away, and above it is an organ, not always displayed, and of which Mr. Gosse was for¬ tunate enough to discover the use. This eminent naturalist likens it to the circular ventilator some¬ times inserted in windows, and he found it was the machine for making the yellow ornamental bricks of which the tower is composed. Pellet by pellet, or brick by brick, does the Melicerta build her house, which widens gradually from the foundation to the summit, and every layer is placed with ad¬ mirable regularity.
In order to obtain the materials for her brick- making the Melicerta must have the power of modifying the direction of the ciliary currents, so as to throw a stream of small particles into the
MELICERTA RINGENS.
93
mould, which is a muscular organ, and capable of secreting a waterproof cement, by which they are fastened together. The result is, not to produce anything like the tubes made by the caddis- worms out of grains of sand, but entirely to change the appearance of the materials employed. All large particles are rejected, and only those retained which will form a homogeneous pulp with the viscid se¬ cretion; and when the process is complete the head of the creature is bent down, and the pellet de¬ posited in its appropriate place. Each pellet appears originally to possess a more or less conical figure, but when they are squeezed together to make a compact wall they all tend to a hexagonal form, by which they are able to touch at all points, and any holes or interstices are avoided.
According to Professor Williamson the young Melicerta commences her house by secreting “a thin hyaline cylinder,” and the first row of pellets are deposited, not at the base as would be expected, but in a ring about the middle of the tube. “At first new additions are made to both extremities of the enlarging ring; but the jerking constrictions of the animal at length force the caudal end of the cylinder down upon the leaf, to which it becomes securely cemented by the same viscous secretion as causes the little spheres to cohere.”
Round the margins of the lobes or expansions
94
MAUVELS OP POND-LIFE.
may be seen delicate threads towards which others radiate; these are thought bv Mr. Gosse to be portions of a nervous system, and two calcars or feelers serve as organs of relation. The young Melicertas are likewise furnished with a pair of eyes, which are probably rudimentary, and disappear as they grow up.
The Melicerta tubes, being large enough to be vis¬ ible to the naked eye, are easily crushed in the live- box, and to avoid this, they are conveniently viewed in a shallow glass cell, covered up as before des¬ cribed. By occasionally changing the water one may be kept for days in the same cell, and will reward the pains by frequently exposing its flower¬ like head. Usually the horns or feelers come out first, and then a lump of flesh. After this, if all seems right, the wheels appear, and make a fine whirlpool, as may be lead ily seen by the use of a little indigo or carmine.
The Melicerta is, however, an awkward object to undertake to shew to our friends, for as they knock at the door she is apt to turn sulky, and when once in this mood it is impossible to say when her fair form will re-appear. At times the head is wagged about in all directions with considerable vehemence, playing singular antics, and distorting her lobes so as to exhibit a Punch and Judv
•r
profile. When these creatures die they leave their
EPISTYLIS.
95
tubes, which are often found empty in tlie ponds they frequent. The Melicertas are conveniently viewed with a power of from sixty to one hundred linear, and a colony of them may be kept alive for some weeks in a glass jar or tank.
Among the remainder of my tiny captives were
Epistylis.
two beautiful members of the Vorticella family, Epistylis and Carchesium. The reader will remember that in the Vorticella previously described, the bells stood upon stalks that were very flexible, and re¬ tractile by means of a muscle running down their
j o
96
MARVELS OF POND-LIFE.
length. The Epistylis is, as its name imports, the dweller on a pillar. The stem is stiff, or only slightly flexible, and has no apparatus by which it can be drawn down. The specimen mentioned stood like a palm-tree, and the large oval bells drooped elegantly on all sides, as its portrait will shew. At times they nodded with a rapid jerk.
The Carchesium differs from the common Vorti- cella , by branching like a tree, but the stems are all retractile, although the trunk seldom exercises the power. A group of these creatures presents a spectacle of extraordinary beauty — it looks like a tree from fairy -land, in which every leaf has a sentient life. In general structure the bells of the E, ns tills and the Carchesium resemble the common Vorticella , and like them may be seen with a power of about one hundred linear for general effect, and with a higher one for the examination of special points. Pritchard notices three species of Car- chesium , and eighteen of Epistylis ;* some of which it is to be hoped will turn out to be only varieties.
Towards the end of this month rotifers abounded, and polyps were plentiful. Among the rotifers was
* Au interesting Epistylis, called Digitalis, from its bells re¬ sembling fox-glove flowers in shape, occurs as a parasite upon the Cyclops quadricornis, a very common entomostracau in fresh-water ponds. At this moment I have a beautiful specimen, branching like a bushy tree, and attached to the tail of a Cylops, who can scarcely move under his burden, which is like Sinbad’s “Old Man of the Sea.”
Carchesium polypmum.
EGGS OF HOT r FEUS.
i>7
one about a two-hundredth of an inch long, pro¬ tected by a carapace, and having a tail terminating in a single style, hence called “Monostyle.” There is perhaps no class of creatures that present so many curious and unexpected forms as the rotifers ; and although we have noticed a good many, there are far more that remain to be found and de¬ scribed.
The water in which the preceding animals dwelt was enlivened by the jumps of the Halteria , a little globe surrounded by long fine cilia, with which its movements were effected; and its companion Avas the Aspidisca lynceus , an oval animalcule, having a distinct cilia or 1 orica, and furnished, in addition to cilia, with bristles, which enable it to walk and climb as well as swim.
There were also some eggs of rotifers attached to the water-plants, in which motion could be de¬ scried at intervals, and a little red eye observed. These eggs are always large in proportion to the creatures that lay them, and if they escape being devoured by enemies, may be watched until their contents step forth.
In this, as in other months, omission is made of creatures that have already come under notice, or our list would assume larger dimensions.
H
CHAPTER VIE
JUNE AND JULY.
LIXDIA TORULOSA— (ECISTES CRYSTALLINES — A PROFESSOR OF DEPORTMENT ON STILTS— PEII LODINA— CHANGES OF FORM AND HABITS— STRUCTURE OF GIZZARD IN PHILODINA FAMILY — MR. GOSSE’S DESCRIPTION-MOTIONS OF ROTIFERS— INDICA¬ TIONS OF A WILL— REMARKS ON THE MOTIONS OF LOWER CREATURES— VARIOUS TPIEORI ES— POSSIBILITY OF REASON- REFLEX ACTIONS— BRAIN OF INSECTS— CONSENSUAL ACTIONS —APPLICATIONS OF PHILOLOGICAL REASONING TO THE MOVEMENTS OF ROTIFERS AND ANIMALCULES.
CHAPTER VIE
.JUNE AND JULY.
A PRESSURE of other occupations prevented full use being made of June and July, nor was the weather of 1860 at all propitious. For this reason the microscopic doings of these two months are recorded in one chapter.
As usual the Kentish Town ponds were productive of objects, and among them were several rotifers not found in the previous months. The first of these was a very small worm-like thing, with one eye, a tuft of cilia about the mouth, and two toes at the tail end. Had it not been for the jaws, which were working like fingers thrust against each other, and which were unmistakably of the rotifer pattern, the animal might have been supposed to belong to some other class. According to the “Micrographic Dictionary,” the Lindia torulosa is 1-75" long, but this specimen was only about 1-200" It was possibly very young, and did not
102
MARVELS OF POND-LIFE.
thrust out its cilia in two distinct tufts, as Cohn describes, although it may have had the power of doing so. At times it sprang quickly backwards and forwards, bringing its head where its tail was before. This object required for its comfortable elucidation a power of about six hundred linear.
Among the common water-plants, which are worth examining as the probable abodes of rotifers or infusoria, is the pretty little thing called “star- weed,” some of which was obtained from the last- mentioned ponds, and on examination yielded a
(ECISTES.
103
specimen of a tube-dwelling rotifer, the (Ecistes crystaJlinus , which, although less beautiful than the Floscules or the Melicerta, is, nevertheless, a pretty and interesting object. In this instance a little rough dirty tube, about 1-70" long, was observed to contain an animal capable of rising up and expanding a round mouth garnished with a wreath of cilia; while a little below, the indefati¬ gable and characteristic gizzard of the tribe was in full play. A power of two hundred and forty linear sufficed to afford a good view, and it was seen that a long, irregular, conical body was supported upon a short wrinkled stalk. The usual drawings repre¬ sent this creature with a short bell-shaped body upon a very long slender pedicle. Possibly this one might have been able to shew himself under this guise, but he did not attempt it; his appearance being always pretty much as described, which made the foot shorter and the body longer than the measurements which naturalists have given, and according to which the whole creature is 1-3G'7 long, although the body is only 1-140". The tube of the (Ecistes is called a “lorica,” or carapace; but it has in truth no right whatever to the appellation.
Another strange rotifer, of whose name I am uncertain, had an ovalish oblong body, and a pair of legs like compasses, twice as long as himself.
104
MARVELS OF POND-LIFE.
His antics were those of a posture-master, or “Pro¬ fessor of Deportment” on stilts. Sometimes he stood holt upright, bringing his legs close together; then they were jauntily crossed, and the hody carried horizontally; then the two legs would be slightly opened, and the body thrown exactly at right-angles to them. These antics were repeated all the while the observation lasted, and had a very funny effect in proving that drollery is practised, if not under¬ stood, in the rotatorial world.
Another kind of rotifer was abundant — the Philodina , which belongs to the same family as the common wheel-bearer, namely, the Philodinwci. The Philodina is a good deal like the common wheel- bearer, or Rotifer vulgaris, but is usually of a stouter build, and carries his eyes in a different place. In the common rotifer tliese organs are situated on the proboscis, while those of the Philodina are lower,
PHI LODI N A.
105
and said to be “cervical.” The changes of form in this rotifer are still more remarkable than in the common wheel-bearer. When resting it resem¬ bles a pear-shaped purse, puckered in at the mouth. Then it thrusts out its tail-foot, swells its body to an oval globe, protrudes its feeler, and slightly exposes a row of cilia. After this two distinct wheels are everted, and as their cilia whirl and spin, the animal is swiftly rowed along, until it thinks proper to moor itself fast by the tail-foot,
I’hilodina — crawling.
and employ all its ciliary power in causing currents to converge towards its throat. When it pleases it can elongate the body, till it becomes vermiform, and it walks like the common rotifer, by curving its back, and bringing its nose and its tail in contact with the ground.
Tiie gizzard of this family ( Philodmcea) presents a considerable deviation from the perfect form ex¬ hibited by the Brachions. According to Mr. Gosse, “The mallei and the incus (terms already explained,)
100
MARVELS OF POND-LIFE
are soldered together into two suhquadrantic-globular masses, which appear to he muscular, but invested with a solid integument. The manubria (handles) may still he recognised in a vertical aspect as three loops, of which the central one is chiefly developed, and in a vertical aspect as a translucent reniform (kidney-shaped) globe.” These descriptions are not easy to understand, not from any want of clearness or precision in the words employed, but from the complicated character of the organ, and its very different appearance under different aspects. To make the matter more intelligible, Mr. Gosse adds, “the structure and action of an apparatus of this type may be made more clear by a homely illus¬ tration. Suppose an apple to be divided longitu¬ dinally, leaving the stalk attached to one half. Let this now be split again longitudinally so far as the stalk, but not actually separating either portion from it. Draw the two portions slightly apart, and lay them down on their rounded sur¬ faces. They now represent the quadrantic masses in repose, the stalk being the fulcrum, and the upper surfaces being crossed by the teeth. By the contraction of the muscles, of which they are com¬ posed, the two segments are made to turn upon their long axis, until the points of the teeth are brought into contact, and the toothed surfaces rise and approach each other. The lower edges do not
MOVEMENTS OF ANIMALCULES.
107
however separate as the upper edges approach, hut the form of the mass alters, becoming more lenti¬ cular, so that when the toothed surfaces are brought into their closest approximation, the outline has a subcircular figure. It is on account of this change of form that I presume the masses themselves to be partially composed of muscle.”
These remarks, although specially made of the Rotifer macrurus , are in the main applicable to all the Philodinns, but the student must not expect to understand any of the complicated gizzards of the rotifers without repeated observations, and no small exercise of patience. It is common to call the portions of the Philodine-pattern gizzard “stirrup¬ shaped;” but Mr. Gosse has shewn them to be quadr antic , that is, shaped like the quadrature of a sphere.
As we are not very well off with subjects for description in these two months, we can afford a little time to consider a question that continually arises in the mind, on viewing the movements of animalcules, and especially of any so highly devel¬ oped as the rotifers, namely, to what extent motions which appear intelligent, are really the result of anything like a conscious purpose or will. When any of the lower animals — a bee, for example — acts in precisely the same way as all bees have acted since their proceedings have been observed, we settle
108
MARVELS OF POND-LIFE.
the question by the use of the term instinct. Those who take the lowest view of insect life, assume that the bee Hies because it has wings, but without wishing to use them, and that the nerves exciting them to action are in their turn excited, not by volition, but by some physical stimulus.
The sight or the smell of flowers is thought by the same reasoners to be capable of attracting the insect, which is unconscious of the attraction, while proximity of food stimulates the tongue to make the movements needful for its acquisition, and so forth. The cells, they tell us, are built according to a pattern which the earliest bee was impelled to con¬ struct by forces that bore no analogy to human reason and human will, and so originate all the ordinary processes of bee life. Sometimes, however, it hap¬ pens that man or accident interposes particular obstacles, and forthwith there appears a particular modification of the orthodox plan, calculated to meet the special difficulty. How is this? Hoes any one of the difficulties which the bee or the ant is able to get over, produce precisely that kind of electrical disturbance, or polar arrangement of nerve particles that is necessary to stimulate the first step of the action by which the difficulty is surmounted; and does the new condition thus established stimulate the second step, and so forth, or can the bee, within certain limits, really think , design, and contrive?
REFLEX ACTIONS.
109
No questions are more difficult of solution; but while protesting against a tendency to undervalue all life below that of man, we must remember we have in our bodies processes going on which are not the result of volition, as when the blood circu¬ lates, and its particles arrange themselves in the pattern required to form our tissues and organs, and also that many of our actions belong to the class termed by physiologists, “reflex,7’ that is, he result of external impressions upon the nervous system, in which the sentient brain takes no part. Thus when a strong light stimulates the optic nerve, the portion of brain with which it is connected in its turn stimulates the iris to contract the pupil; and it is supposed that after a man has begun to walk, through the exercise of his will, he may continue to walk, by a reflex action ; as his feet press the ground they transmit an impression to the spinal cord, and the legs receive a fresh impulse to locomotion, al¬ though the mind is completely occupied with other business, and pays no attention to their proceedings. # The ordinary movements of insects appear to be of this character, and to be excited by the ganglia belonging to the segment to which the moving limbs are attached. Thus a centipede will run, after its head has been cut off, and a water-beetle (] )ytiscus) swam energetically when thrown into water after * See Carpenter’s “Manual of Physiology.”
110
MARVELS OF FOND-LIFE.
its brain had been removed.*
It must not, however, be assumed that the brain of insects has nothing to do with their movements. It is the means of co-ordinating or directing them to a common end, and gives rise to what are called consensual motions, that is, movements which are accompanied or stimulated by a sensation, although not. controlled by a will. In man these actions are frequently exhibited, uas when laughter is pro¬ voked by some ludicrous sight or sound, or by the remembrance of such at an unseasonable time.”f Sneezing is another instance of a sensation leading to certain motions, without any intervention of the human will.
Speaking of these consensual actions, Dr. Car¬ penter observes, “It is probable, from the strong manifestations of emotion, exhibited by many of the lower animals, that some of the actions which we assemble under the general designation of in¬ stinctive are to be referred to this group.”
A special volume would be required for anything like a complete examination of the little which is known on this subject, but these few remarks may assist the microscopic beginner in examining the movements of his subjects, and guard against the error of referring to reason and volition those which are, probably, either the direct result of stimulants
* Carpenter’s Manual of Physiology, p. 551. f Ibid, p. 543.
MOVEMENTS OF ROTIFERS.
Ill
applied to the surface, (as in nerveless creatures,) or the indirect (reflex) result of such stimulants in beings like the rotifers, who have a nervous svstem; or the result of sensations , which excite actions without previously referring the matter to the decision of a will. It must not, hoAvever, be too readily assumed that the behaviour of creatures possessing distinct organs is entirely automatic; and we must not forget that even the best physiologists know very little concerning the range of functions which the nervous ganglia of the invertebrata are able to discharge.
CHAPTER VIII.
AUGUST.
MUD COLOURED BY WORMS— THEIR RETREAT AT ALARM— A COUNTRY DUCK-POND -CONTENTS OF ITS SCUM— CRY PTO- MON ADS— THEIR MEANS OF LOCOMOTION— A TRIARTHRA (THREE-LIMBED ROTIFER)— THE BRACHION OR PITCHER ROTIFER— ITS STRIKING FORM — ENORMOUS GIZZARD — CILIARY MOTION INSIDE THIS CREATURE— LARGE EYE AND BRAIN— POWERFUL TAIL— ITS FUNCTIONS— EGGS.
I
CHAPTER VIII.
AUGUST.
In the beginning of this month a pond in the Finchley Road, a little beyond the Highgate arch¬ way, supplied some more specimens of the Pterodina patina , described in a previous chapter; but towards the middle of the month a visit to Chipstead, in Surrey, enabled a new region to be explored.
It is always a treat to a Londoner to get down to any of the picturesque parts of Surrey ; the trees exhibit a richness of foliage and variety of colour not seen within the regions of metropolitan smoke; the distance glows with the rich purples so much admired in the pictures of Linnel, and the sun-sets light up earth and sky with the golden tints he is so well able to reproduce. Probably the warmth of the soil, and the purity of the air, may make Surrey ponds prolific in microscopic life; but of this we do not know enough to make a fair com¬ parison, although our own dips into them were tolerably lucky.
116
MARVELS OF POND-LIFE.
Walking one day down a lane leading towards Reigate, where the trees arched overhead, ferns grew plentifully in the sandy banks, and the sunlight flitted through the branches, and chequered the path, we came to a shallow pond, or great puddle, which crossed the way, and near the edge of the water the eye was struck with patches of crimson colour. On attempting to take up a portion of one of these patches the whole disappeared, although when the disturbance ceased, the rich colour again clothed the dingy mud. The appearance was caused by thousands of little worms, belonging to the genus Tubifex , not uncommon in such situations, who thrust themselves out to enjoy the light and air, and retreat the moment an alarm is given. Pro-
o
bablv both actions belong to the class described in the last chapter, as “reflex;” but it would be in¬ teresting to know whether creatures so humble have any sense of fear. These worms will repay obser¬ vation, but in these pages we eschew all their tribe, — unless the rotifers be assigned to them — and take ourselves once more to our especial subjects.
Knowing that farm-ponds are usually well stocked with microscopic game, we made a dip into one more especially assigned to ducks, and obtained wondrous little for our pains. We were not, how¬ ever, discouraged, but made an examination of the circumstances, which determined a particular course
A COUNTRY DUCK-POND.
117
of action. Our piece of water was simply a dirty duck-pond, in which no large plants were growing, and which did not even exhibit the little disks of duckweed, that are common to such situations. There was, however, on the surface, in parts, an exceedingly tine scum of pale yellow green, and
9 0 0
Cryptomonad — Euglen a.
this, armed with a tea-spoon, we proceeded to attack. By careful skimming, a small bottle was half-tilled with minute organic particles, which were likely to be interesting in themselves, and pretty sure to be the food for something else. A small drop was placed on a tablet of the live-box, flattened out by the application of the cover, and viewed with a power
118
MARVELS OF POND-LIFE.
of two hundred linear, which disclosed swarms of brilliant green globes, amongst which were a good sprinkle of minute creatures, like the Euglence already described, and whose little red eyes contrasted vividly with the prevailing emerald hue.
One of the higher infusoria, whose species I could not identify, was devouring them like a porpoise among sprats. It did not, however, exhibit any sense in its hungry career; it moved about in all directions, gulping down what came in its way,
Cryptomonad.
but often permitting the escape of the little green things, that were almost in its mouth. The little globes rolled and whirled about without the faintest indication of a purpose, and without exhibiting any instrument with which their locomotion was effected. To find out how this was done, a higher power was used, and from their extreme minuteness an ampli¬ fication of seven hundred and twenty linear was conveniently employed, although a lower one (three or four hundred) disclosed the secret by shewing
CRYPTOMONADS.
11<)
that a little whip was nourished about through the neck, which the lower power revealed. When highly magnified, each little globe was seen to con¬ sist of an outer case of a reddish orange colour, which was noticeable on looking at the edges, al¬ though in the centre it was transparent enough to shew the brilliant green contents, that resembled the chlorophyl, or green colouring matter of plants. From a short neck proceeded the whip-like fila¬ ment, which was lashed and twisted about in all directions. These little creatures belong to the monad family, but whether they are to be called Trachelomonads , or by some other hard name the learned must decide.
The “Micrographic Dictionary” puts a note of interrogation to the assertion of some writers that Trachelomonads have no necks, and draws some with such an appendage.
Pritchard’s last edition is against necks, and whether the necks or no necks are to win, is a mighty question equal at least to the famous contro¬ versy, which divided the world into “big and little endians in the matter of breaking eggs.”
A discussion of more importance is, whether these Crijptomonads — that name will do whatever comes of the neck controversy — are animals or vegetables. Lachmann and Mr. Carter affirm that they have detected a contractile vesicle, which would assimulate
1^0 MARVELS OF POND-LIFE.
them to the animal series, hut their general beha¬ viour is vegetable; and the “Micrographic Dictionary” is in favour of referring them to the Algce — that great family of simple plants, of which the sea- weeds are the most important representatives.
When anv of the monads swarm, there are sure to he plenty of other creatures to eat them up, and in this instance the predaceous animalcule, already described, was not the only enemy the little
green globes had to suffer from, as two sorts of rotifer were frequently met with. One of these was a very handsome and singular creature, which in some positions had the general contour of a cocka¬ too, only that the legs were wanting, and the head exhibited a monkey face. The “wheels” were re¬ presented by ciliary tufts, and two bright red eyes twinkled with a knowing look. From each shoulder proceeded a long curved spine, and about two-thirds
CILIARY MOTION.
121
down the body, and lying between the two long spines, a shorter one was articulated, which followed the same curve. A gizzard was busy in the breast, and the body terminated in two short toes, which grasped a large round egg. Whenever the cilia were drawn in, the three spines were thrown up; but they had an independent motion of their own, and every now and then were jerked suddenly and violently back, which occasioned a rapid change in the creature’s position. The gizzard appeared to consist of two rounded masses, having several ridges or teeth, which worked against each other something like the prominences of a coffee-mill. From the three spines, this animal was a Tnarthra , or Three-limbed Rotifer, but the position of the spines, and the toes, made it differ from any species described in the “Micrographic Dictionary,” or in Pritchard.
Whether or not this species is to be regarded as having a lorica or not, must depend upon the pre¬ cise meaning attached to that word. At any rate the integument was much firmer than in many of the rotifers, and gave an efficient support to the spines which a mere skin could not do. As Mr. (fosse remarks of an allied genus, the Polyarthra , or Many-limbed Rotifer, this creature could not be investigated without coming to the conclusion “Here again we have true jointed limbs;” a fact of great importance in determining the zoological rank of
MARVELS OF POND-LIFE.
1 OO
1 <v iv
the family, and in supporting Mr. Gosse’s view that they belong to the group of Arthropoda , of which the insects are the principal representatives.
Brachionus urceolaris.
This drawing has been accidentally reversed by the engraver, which alters the relative place of the internal organs.
Another rotifer of even greater interest, which was busy among the Cryptomonads, was the Brachion, or “Pitcher Rotifer,” (Brachionus.) The members
PITCHER ROTIFER.
123
of this genus will frequently reward the searcher into pond-life. Their main characteristic is a cup or pitcher-shaped lorica, which is cut or notched at the top into several horns or projections, the number of which indicates the species; while two or more similar projections ornament the bottom. This lorica is like the shell of a tortoise open at both ends ; from the top an extremely beautiful wreath of cilia is protruded, and also some longer and stiff cilia, or slender spines, which do not ex¬ hibit the rotatory movement. The ciliary apparatus is in reality continuous, but it more often presents the appearance of several divisions, and the lateral cilia frequently hang over the sides. From the large size of each cilium they are very favourable creatures for exhibiting the real nature of the action, which gives rise to the rotatory appearance, and which can be easier studied than described. By movements, partly from their base, and partly arising from the flexibility of their structure, the cilia come alternately in and out of view, and when set in a circular pattern, the effect is amazingly like the spinning round of a wheel. The internal arrangements of the Brachiones are finely displayed, and they have a most aldermanic allowance of gizzard, which extends more than half-way across each side of the median line, and shows all the portions described by Mr. Gosse. As the joints of this machine move, and
124 MARVELS OF POND-LIFE.
the teeth are brought together, one could fancy a sound of mill-work was heard, and the observer is fully impressed with a sense of mechanical power.
When the creature is obliging enough to present a full front view, her domestic economy is excellently displayed. The prey that is caught in her whirl¬ pool is carried down by a strong ciliary current to the gizzard, which may be often seen grappling with objects that appear much too big for its grasp; and Mr. Gosse was lucky in witnessing an attempt to chew up a morsel that did actually prove too large and too tough, and which, after many inef¬ fectual efforts, was suddenly cast out. As soon as food has passed the gizzard, it is assisted in its journey by more ciliary currents, which are noticeable in the capacious stomach, in the neighbourhood of which the secreting and other vessels are readily observed. Just over the gizzard blazes a great red eye, of a square or oblong form, and it reposes upon a large mass of soft granular-looking brain, which well justifies Mr. Gosse’s epithet “enormous.” Whether this brain is highly organized enough to lie a thinking apparatus, we do not kqow, but it is evidently the cause of a very vigorous and consen¬ taneous action of the various organs the Brachion possesses.
A description of the Brachion would be very incomplete if it omitted that important organ the
EGGS OF BRACHIONES.
125
tail, which in this family reaches the highest point of development. It is a powerful muscular organ, of great size in proportion to the animal, capable of complete retraction within the carapace, and of being everted wholly, or partially, at will. It ter¬ minates in two short conical toes, protruded from a tube-like sheath, and capable of adhering firmly even to a substance so slippery as glass. This tail may be observed to indicate a variety of emotions, if we can ascribe such feelings to a rotifer, and it answers many purposes. Now we see it cautiously thrust forth, and turned this way and that, exploring like an elephant’s trunk, and almost as flexible. Now it seizes firm hold of some substance, and anchors its proprietor hard and fast. A few mo¬ ments afterwards it lashes out right and left with fury, like the tail of a cat in a passion. Then again it will be retracted, and a casual observer might not imagine the Brachion to be furnished with such a terminal implement.
The Brachiones mav often be seen with one or
%/
more large eggs stuck about the upper part of the tail, and others may be discerned inside. One specimen before us has three eggs attached to her in this way. They are large oval bodies, with a firm shell. These creatures differ very much in ap¬ pearance, according to the direction in which they are seen, and a side view makes them look so dif-
126
MARVELS OF POND-LIFE.
ferent from a full front or back aspect, that it would be easy to suppose another animal was under observation. The extent to which the ciliary appara¬ tus is protruded, and the pattern it forms likewise differs continually; and hence no drawing, however correct, is sure to resemble the arrangement that may be presented to the observer’s eye. But how¬ ever our little uPitcher” may be viewed, it is sure to prove a spectacle of interest and delight.
CHAPTER IX
SEPTEMBER.
MICROSCOPIC VALUE OF LITTLE POOLS— CURIOUS FACTS IN APPEARANCE AND DISAPPEARANCE OF ANIMALCULES AND ROTIFERS— MODE OF PRESERVING THEM IN A GLASS JAR- FRAGMENTS OF MELICERTA TUBE— PECULIAR SHAPE OF PELLETS— A MPHILEPTUS—SCARIDIUM LONGICAUDUM— A LONG TAILED ROTIFER-STEPHONOCEROS EICHORNII— A SPLENDID ROTIFER— ITS GELATINOUS BOTTLE— ITS CROWN OF TEN¬ TACLES— RETREATS ON ALARM— ILLUMINATION REQUISITE TO SEE ITS BEAUTIES— ITS GREEDINESS— RICHLY-COLOURED FOOD— NERVOUS GANGLIA.
CHAPTER IX.
SEPTEMBER.
Scattered about Hampstead Heath are a number of little pools, not big enough to be dignified by the name of ponds. They are generally surrounded by furze bushes, and would escape attention if not actually looked for. Those which are mere puddles, and have only a brief existence in rainy weather, seldom reward the labour of investigation; but others are permanent, except after prolonged drought, and afford convenient situations for the growth of con¬ fervas, star-weed, and other plants. These will nearly always repay the microscopic collector during the winter, when he must break the ice to get at their contents; in spring, when long chains of frog-spawn afford ocular evidence of the prolific properties of the Batrachian reptiles; and in summer, when they afford both shade and sunshine to their numerous inhabitants. Small beetles, water-spiders, larvae of gnats, and other insects, rotifers, including the tu- bicolar sorts, and several varieties of infusoria may
130
MARVELS OF POND-LIFE.
l)e expected and generally found. There is, however, a curious fact about ponds, big and little, which Pritchard remarks upon in his “Infusoria,” and which corresponds with our own experience, that those which have proved to be well stocked with any particular creature during one year, will very likelv contain none of it in the next. There are of course exceptions to this rule, but we have often been astonished and disappointed at finding the complete change, both in populousness and popula¬ tion, that a revolution of twelve months will make; and it would be extremely interesting to notice the changes that took place during a term of years.
Such researches might unfold some unexpected laws in the succession of infusorial life. Those germs which are most widely diffused, will be the most likely to be developed in any mass of convenient water; but how and why the rarer forms come and go is very imperfectly understood. Slight modifi¬ cations in surrounding circumstances will materially affect the result. Thus, if we bring home a handful of conferva, and a few water-plants of higher or¬ ganization, such as duck-weed and anacharis, and place the whole in a glass jar full of pond-water, we shall at first have a good stock of objects ; but tliev will usually grow less and less, until scarcely anything is left. If, however, we introduce a few pieces of straw, or a tiny wisp of hay, we shall
ANIMALCULE TANK.
131
succeed much better, and not only preserve our population longer, but enjoy a succession of animated crops. Extensive decomposition of vegetable matter kills off all but certain families, such as Paramecia, who enjoy it; on the other hand, too little decom¬ position proves fatal to some creatures, by depriving them of their food, and when they have died off, those avIio depended upon them for a living, die too. Different vegetables in decomposition suit dif¬ ferent creatures, and hav and straw in that state seem to please the largest number. An animalcule tank will succeed best when it contains two or three kinds of growing plants, which oxygenize the air, and a moderate variety of decomposing organ¬ isms will supply food without making the water offensive.
From these considerations it will be apparent that not only the nature of the vegetation of a pond, which is often changed by accidental circumstances, but also the quality of the odds and ends that the winds may blow into it, or which may fall through the air, will do much to determine the character and numbers of its inhabitants, while the quantity of shade or sunshine it enjoys, will also exercise an important influence. Ilay and other infusions have from the beginning of microscopic investigations been employed to obtain : creatures which the Germans call “Infusions thierchen,” (In-
132
MARVELS OF POND-LIFE.
fusion animalcules,) and the English “Infusoria;” but verv little has yet been done in the way of their scientific culture and management.
To return from this digression to our little Hamp¬ stead ponds, we obtained from one, in September, that was full of star-weed, a number of sugar-loaf bodies adhering to one another, and of a pale yellow brown colour. The specimens first examined looked complete in themselves, and were taken for eggs of some water creature. Further search however dis¬ closed aggregations of similar sugar-loaves that had evidently formed part of a tubular structure, and the idea at once occurred that they were fragments of a Melicerta tube, a conclusion that was verified by finding some tubes entire and a dead Melicerta in the rubbish at the bottom. All the specimens of Melicerta tubes we had hitherto examined were com¬ posed of rounded pellets, but these were made of pointed cones or sugar-loaves, with the points pro¬ jecting outwards from the general surface. In Pritchard’s “Infusoria,” these pellets are described “as small lenticular bodies.” The “Micrographic Dictionary” states that the tubes of the Melicerta are composed of “numerous rounded or discoidal bodies;” and Mr. Gosse, in his “Tenby,” which con¬ tains an admirable description, and an exquisite drawing of this interesting rotifer, calls the pellets “round.”
133
MELICERTA TUBE.
Not being able to obtain a living specimen of the Melicerta, who made her tube of long sugar- loaves, 1 could not tell whether she differed in structure from the usual pattern of her race, but the general appearance of the dead body was the same. It is possible that these creatures possess some power of modifying the form of their singular bricks, or they may at different ages vary the pat¬ terns, which matters some fortunate possessor of a colony of these animals may be able to verify.
In the sediment of the water containing the Melicerta cases was found an animalcule about 1- 120" long, covered with cilia, and having a proboscis seldom more than a quarter of the length assumed by the body, which continually changed its form, sometimes elongating, sometimes shortening, and often contracting one side into a deep fissure. It was, probably, an Amphileptus , though not precisely agreeing with any drawing or description I am acquainted with. Another inmate of the same water was a lively long-tailed rotifer, with a small oval body, a tuft of vibrating cilia and a curved bristle visible among them on one side. This creature had a jointed tail-foot, ending in two long style-shaped toes, and by means of this appendage executed rapid leaps or springs. It was the Scaridium longicaudum , and agreed in dimensions tolerably well with the size given in the books, namely, total length 1-72". With
134
MARVELS OF POND-LIFE.
a power of five hundred diameters the muscles of the tail-foot presented a beautifully striated appearance.
Towards the end of the month I passed the Yale of Heath Pond, Hampstead, and although I had
not gone out for the purpose of collecting, was
fortunately provided with a two-dram bottle. Close by the path the Anacharis alsinastrum grew in
profusion, quantities of water-snails crawled among its branches, and small fish darted in and out,
threading their mazes with lightning rapidity.
Thrusting a walking-stick among the mass of vege¬ tation, a few little tufts were drawn up and care¬ fully bottled, with the addition of a little water. Returning home, a few leaves were placed in the live-box, and on examination with a power of sixty diameters they disclosed a specimen of, perhaps, the most beautiful of all the rotifers, the Stephanoceros Eichornii. In this elegant creature an oval body, somewhat expanded at the top, is supported upon a tapering stalk, and stands in a gelatinous bottle,
V
S tephanoceros Zichorrm
STEPHANOCEROS.
135
composed of irregular rings superimposed one upon the other, as if thrown off by successive efforts, the upper ones being inverted and attached to the body of the animal. But that which constitutes the glory of this little being is a crown of five tapering ten¬ tacles, each having two rows of long cilia arranged on opposing sides, but not in the same plane. The ordinary position of the tentacles is that of a graceful elliptical curve, first swelling outwards, then bending inwards, until their points closely approximate, but each is capable of independent motion, and they are seldom quiet for many minutes at a time. The cilia can be arranged in parallel rows or in tufts at the will of the creature, and their motion appears under control, and susceptible of greater modifica¬ tion than is exhibited by the ordinary infusoria.
The Stephanoceros is a member of the Floscule family, but in all the specimens I obtained and watched for several weeks, there was an important difference in the relation of the tube to the creature. In the Floscules I had never seen anything like an adhesion between the tube and the animal, but in the Stephanoceros I noticed it continually, and always in the manner already described. Like the Floscule, the Stephanoceros .is readily alarmed, and retreats into her house, carrying with her the invaginated portion. In the last edition of “Pritchard’s Infu¬ soria,” this case is spoken of as apparently not
MARVELS OF POND-LIFE.
1-36
tubular, but a solid gelatinous mass, enveloping the animal as high up as the base of the rotary arms. It is very likely that specimens at different ages, and possibly in different seasons, may vary in the structure of their abodes; but I am not able to concur in the preceding account, as all the tubes I examined resembled sacks turned in at the mouth, and attached to the shoulders only of their inmates; and on one occasion I was able to look down into a deserted tube, which had not collapsed, as it would have done if it had been merely a solid gelatinous mass.
Like the Floscule, the Stephanoceros only reveals her beauties under careful illumination. A direct light renders them invisible, and only when the requisite obliquity has been obtained, does the ex¬ quisite character of the structure become displayed. The dark-ground illumination is very useful, and makes the cilary action very distinct. At times a view can be obtained, in which the cilia of perhaps a single tentacle are all ranged like the steel springs of a musical box. For a moment they are quiescent, and then they vibrate in succession, each moving thread sparkling in the light. With a clumsy mode of lighting them, the cilia look like stumpy bristles, and are often so drawn; but precisely the right quantity of light coming in the right direction, makes them appear more numerous, and much longer
CROWN OF TENTACLES.
i.r
than would at first be supposed. When well ex¬ hibited the tentacles have a lustre between glass and pearl ; the body, in a favourable specimen, is like a crystal cup, and the food, usually composed of small red and green globes, glows like emeralds and rubies, as if in the height of luxury the little epicure had more than rivalled Cleopatra’s draught, and instead of dissolving, swallowed its jewelry whole. So lustrous and varied in colour is the whole appear¬ ance of the animal under these circumstances, that it is frequently alluded to by one of our first artists, to whom it was displayed.
It is said by some authors that the tentacles are used to seize prey. This never occurred under my observation, although their basal portions are often approximated when an object is forced down to the grinding apparatus below. The Stephanoceros is a ravenous feeder, and swallows a variety of creatures. Green vegetable monads, rich red and brown globes of similar characters, and any animalcule that comes in her way is acceptable; and even good-sized rotifers do not escape her all-consuming maw. On one oc¬ casion I noticed one of the loricated sort, more than half as long as one of her tentacles, rapidly swal¬ lowed, and passed downwards without attempting to escape. Objects much too big for the gizzard are often gulped down, and probably receive a pre¬ liminary softening and maceration in the crop. Very
MARVELS OF POND-LIFE.
138
often, when food is plentiful, the creature is filled to the brim, but still endeavours to continue her abundant meal. From the presence of large quan¬ tities of food and the density of the integuments, the gizzard cannot always be seen; but in favourable specimens its teeth may be observed busily at work.
At the base of the tentacles small masses of matter may be discovered, which are probably ner¬ vous ganglia, and other organs ; and Ehrenberg discovered small vibrating bodies, supposed to be connected with the function of respiration. A single egg, as shewn in the annexed drawing, is often found, and the ovarium is said to develop but few at a time. Two red eyes are found in young specimens, but in adults they either disappear or are not conspicuous. The Stephanoceri are sociable animals, and ivhen one is found, others are probably near at hand. Several may often be discovered on the same branch of a small water-plant, of various, dimensions, and in different stages of growth. The full size is about 1-3G" in height, and from its magnitude care is required not to crush it in the live-box. When specimens are plentiful, some should be placed in that convenient receptacle; and others with the plant on which they are growing, in a glass cell or trough, where they have more room to display their motions, and can with fresh
supplies of water, be preserved for days and weeks. With occasional renewals from one pond, 1 was able to keep up a stock for about three months, and never had objects which gave more pleasure to myself, or to my friends.
OCTOBER.
STENTORS AND STEPHANOCERI— DESCRIPTION
OF STENTORS —
MODE OF VIEWING THEM — THEIR ABUNDANCE — SOCIAL HABITS— SOLITARY STENTORS LIVING IN GELATINOUS CAVES —PROPAGATION BY DIVERS MODES— LIMNIAS CEEATOPHYLLI —ANOTHER TUBE-DWELLING ROTIFER— YOUNG AND OLD SPECIMENS— A GROUP OF VAGINICOLJE — CHANGES OF SHAPE —A BUBBLE-BLOWING VORTICELLA.
CHAPTER X.
OCTOBER.
October, the finest of our autumn months, is noted for usually granting the inhabitants of our dripping climate about twenty pleasant sunshiny days, and it is probably on this account somewhat of a favourite with the infusorial world, although the cold of its nights and early mornings thins their numbers, which reach a maximum in the summer heat. Even in the dismal year 1860, October maintained its character, and afforded a great many opportunities of animalcule hunting, during which a constant supply of Stephanoeeri were readily ob¬ tained, together with swarms of Stentors , which are not exceeded in interest by any of the Ciliated Protozoa. The Stentors were abundant on the same weed ( Anacharis ,) that formed the residence of the Stephanoeeri, and might be seen in large numbers hanging from it like green trumpets, visible to the unassisted eye. They belong to the Vorticella family, which has already given us several beautiful objects,
144
MATLVELS OF FOND-LIFE.
and possess a marvellous power of changing their shape. Those before us are named after this pro¬ perty Stentor polymorphic * or Many-shaped Stentors, and owe their exquisite tint to numberless green vesicles, or small cavities filled with colouring matter like that of plants. This, however, is not essential to the species which may often be found of other hues. In size this S ten tor varies from a hundred and twentieth to one twenty-fourth of an inch. It is entirely covered with fine cilia, disposed in longitudinal rows, and round the head is a spiral wreath of larger and very conspicuous cilia leading to the mouth.
Having observed the abundance of these creatures, a few small branches to which they were appended, were placed in the glass trough, and viewed with powers of sixty and one hundred linear. Some had tumbled down to shapeless lumps, others presented broad funnel-shaped bodies; while others stretched themselves to great length like the long, narrow post-horns which still wake the echoes of a few old- fashioned towns. The ciliary motion of the elegant wreath was active and rapid, causing quite a stir among all the little particles, alive and dead; and when the right sort of food came near the corkscrew entrance to the mouth, down it went, and if con¬ spicuous for colour, was subsequently seen appa-
* See Frontispiece.
STENT0R
145
rently embedded in little cavities, which Ehrenberg supposed were separate stomachs, although that theory is now seldom received. One advantage of viewing these objects in a sufficient quantity of water, to leave them in freedom, is that they fre¬ quently turn themselves, so that you can see right
A, 15, C, D, Stentor Millleri in different degrees of expansion. A large one twenty-fourth of an inch long.
specimen i*
down into them; and the drawing given in the frontispiece represents such a view, which is the most favourable for the exhibition of the mouth. To make out the details of their structure, to see the nucleus and other organs, the flattening in the live-box is useful, and it enables much higher powers to be employed.
L
146
MARVELS OF PONE-LIFE.
After leaving the Anaclmris in a glass jar for a few days, the Stentors multiplied exceedingly ; some clung to the sides of the vessel in sociable com¬ munities, others hung from the surface of the water, and crowds settled upon the stems, visibly changing their tint, as the Stentor green was much bluer than that of the plant. Scores swam about in all sorts of forms. Now they looked like cylindrical vessels with expanding brims, now globular, now oddly distorted, until all semblance of the original
shape was lost. In many cases they were found
in shiny tubes, but these were never so lively or green as the free swimmers, but mostly of a dingy dirty hue.
These housekeepers were more timid and cautious than the roving tribe. They came slowly out of their dens, drew back at the slightest alarm, never took their tails from home, and only extended their full length when certain not to be disturbed. Some authors have thought they only take to private lodgings when they feel a little bit poorly, but
others dispute this opinion, and I do not think it is correct. I have found these Stentors at all
seasons, from January to the autumn, but they are never so numerous, nor aggregated in numbers like the roving sort. Whether they are old folks, who are tired of the world and its gaieties, and devote the remainder of their lives to contemplation, or
PROPAGATION BY DIVERS MODES.
147
whether they are bachelors disappointed in love, I am unable to say; but they are very inferior in beauty to the “gay and glittering crowd.”
For some weeks my Stentors abounded, and then most of them suddenly disappeared. They could not have “moved,” but probably “went to smash” by a process peculiar to infusoria, and which Du- jardin politely described as “diffluence.” This mode of making an exit from the stage of life is more tragical than the ripping up so fashionable in Japan. The integument bursts, and its contents disperse in minute particles, that in their turn dis¬ appear, and scarcely leave a “wrack behind.”
The Stentors obey the injunction to “‘increase and multiply” by “self-division, which is either longitu¬ dinal or oblique,”* and the nucleus, which plays such an important part in infusoria, is band-like, monileform, (bead-shape,) or round. When an animalcule increases by self-division, a portion of the nucleus goes with each part, and it is probably the organ which stimulates the change. It is also concerned in other modes of propagation, and it is appropriately called by Owen the “seat of spermatic force.” “The anus is situated on the back close beneath the ciliary circle;” and the “contractile vesicle on a level with the ciliary wreath.” Ac¬ cording to Pritchard and Professor Cienkowski. the
* Pritchard, p. 581.
148
MARVELS OF POND-LIFE.
encysting process takes place in these animalcules, which will thus give another mode of generation by which the germs are produced.
Before closing an account of the Stentor, let us revert a moment to the ciliary wreath, as it may he made the subject of a curious experiment. If, for example, the cilia are viewed at right-angles to their length, they will seem to form a delicate frill, in which a quivering motion is perceived. But if the table is shaken by a sharp blow, the frill is thrown into waves, or takes the form which washer¬ women give to certain female articles by the use of the Italian iron, and the ciliary motion is thus made to take place in different planes, and rendered strikingly apparent.
One day turning over the Anacharis in search of subjects, a small brown tube was noticed, from which a glassy rod protruded like the feeler of a rotifer. Keeping the table quiet, and watching the result, was soon rewarded by a further protrusion of the feeler, accompanied by a portion of the body of the inmate of the tube. The feeler was thrust on this side and on that, as if collecting informa¬ tion for its proprietor, who, I suppose, was satisfied with the intelligence, and gradually extended herself, until she stood out two-thirds in length beyond the tube, and set two lobes of one nearly contin¬ uous ciliary organ in rapid motion. Sometimes the
LIMNIAS C E R A T OPHYLLI.
149
creature, whose name was Limnias ceratopliylli , bent its neck, if I may so speak, to the right, and sometimes to the left, and sometimes stood upright,
Limnias ceratopliylli.
when the true form of the ciliary apparatus could be seen, and it did not deviate very much from a circular form, although the outline given by Mr. Gosse,
150
MARVELS OF POND-LIFE.
in his “Evenings with the Microscope,” approximates to a figure of 8, from the constriction of the middle, and other drawings have the same appearance.
In Pritchard’s book the cause of this discrepancy is explained, and we are told that “the rotary organ is two-lobed when fully grown, being then constricted in the middle,” and that in a young specimen the rotary organ is nearly circular. The Limnias tube was opaque, from the adhesion of foreign matter, and presented an untidy appearance, strangely contrasting with the clear, neat bottles of the Floscules. The length of the Limnias varies, according to Pritchard, from 1-20" to 1-40". Our specimen, when fully extended and magnified one hundred and eighty linear, looked about three inches and a half long, and was therefore verv small. Just below the ciliary lobes the gizzard is seen, with its toothed hammers working one against the other. The masticatory organ differs from the typical form, as represented in the Brachion; and Mr. Gosse observes that “each uncus forms, with its ramus , a well-defined mass of muscle enclosing the solid parts, and in form approaching the quad¬ rature of a globe. Across the upper surface of the mass the uncus is stretched like three long parallel fingers, arched in their common direction, and im¬ bedded in the muscular substances, their points just reaching the opposing face of the ramus , and meeting
COTHURNI A.
151
the points of the opposite uncus when closed, ”*
There is no connection between the Limnias and her tube, except that of simple adhesion, which takes place by means of the end of the foot-stalks.
In a former chapter we have described an inter¬ esting relation of the Vorticella, the Cothurnia, whose elegant crystal vases form a very artistic abode, characterized by possessing a distinct foot. Other species of the same family inhabit vases which have no foot or stalk, or live in gelatinous sheaths less accurately fashioned. Sometimes these creatures are obliging enough to conform to the specific de¬ scriptions which eminent naturalists have given of them, and also to the characters which the authorities have assigned to the different genera in which they have been grouped, but the microscopist will often meet with difficulties in the way of classification. The simplest plan is to consider the group of Vorticella-like animals which inhabit tubes or sheaths, as belonging to the Vorticella family; but it is common to give them a separate name, and designate them as Ophrydina , or Vaginifera , sub¬ divided into genera, to which characteristics are assigned that do not exactly lit a curious assemblage of creatures, that were developed in the water of this month’s collections.
* The term uncus, ramus, etc., have been explained in chapter II, page 37.
MARVELS OF POND-LIFE.
1.32
Attached to a piece of weed were a number of cylindrical masses of brownish jelly, with rounded tops, and situated in an irregular and very trans¬ parent sheath, about twice as high as themselves. Presently they all rose up to four times their pre¬ vious height, put forth a beautiful crown of vibrating
£40
Vaginicola.— (A, elongated; B, retracted.)
cilia, and opened a sort of trap-door to their in¬ ternal arrangements. In this position they had a long cylindrical form, gracefully curved, but of nearly equal width from the mouth to the base, and they readily imbibed particles of carmine, which tinged sundry little cavities with its characteristic
VAGINICOLA.
153
hue. The slightest disturbance caused the ciliary wreaths to be drawn in, and the bodies to be retracted, and descend into their house like a conjuring toy, until the appearance first described was reproduced.
The general form and structure of these objects was like the drawings usually given of Vaginicoln , which is said not to exist in groups, although two individuals are commonly found in one well -shaped cell. These creatures however did not taper towards the base as Vaginicolae generally do, and perhaps they became aware of this defect in their figures, for after a day or two a change appeared, and they assumed a more graceful form by swelling out in the middle, and then growing slender down to the bottom, very much like the pattern given by sdass-blowers to little vases for flowers.
It is very important to note the changing ap¬ pearance of animalcules, and where the same indi¬ viduals can be observed from day to day, these will often be found considerable. It is probable that when such particulars are fully known, the number of species will be greatly reduced, and the study of these organisms considerably simplified. I have called the animals just described VaginicoJw , but the reader must be prepared to find the same sort of bodies, inhabiting well-formed vases, either solitarily or in couples, the latter condition arising
154
MARVELS OF POND-LIFE.
from the fission of one individual without a cor¬ responding division of the abode.
For a few weeks I continually met with groups living as I have described, in what may be called amorphous cells, which were often so nearly like the surrounding water in refracting power, as to be discerned with some difficulty. No trace could be seen of divisions into separate cells, but they all appeared to live happily together in one room, and if one went up all went up, and if one went down all went down, as if their proceedings were regulated by a communitv of sensation or will.
Another little curiosity was a transparent cup upon a slender stem, which stood upright like a wine-glass, and supported on its mouth a transparent globe. By removing a leaf which prevented the stalk being traced to its termination, it was found to be a Vorticella, and after two hours the globe was partially drawn in, and reduced in size. Why the creature was engaged in blowing this bubble I do not know, but it may possibly have been thinking of encysting itself, and was trying the (pialitv of the transparent mucus it had produced.
CHAPTER XT.
NOVEMBER.
CHARACTERISTICS OF THE POLYZOA— DETAILS OF STRUCTURE ACCORDING TO ALLMAN— PLUMATELLA REPENS— ITS GREAT BEAUTY UNDER PROPER ILLUMINATION — ITS TENTACLES AND THEIR CILIA— THE MOUTH AND ITS GUARD OR EPIS- TOME— INTESTINAL TUBE— HOW IT SWALLOWED A ROTIFER, AND WHAT HAPPENED — CURIOSITIES OF DIGESTION— ARE THE TENTACLES CAPABLE OF STINGING P-RESTING EGGS, OR “STATOBLASTS”— TUBE OF PLUMATELLA— ITS MUSCULAR
CHAPTER XT.
NOVEMBER.
During the fag end of last month I observed some fragments of a new creature among some bits of Anacharis, from the Vale of Heath Pond, and searched for complete and intelligible specimens without effect. Luckily one evening a scientific neighbour, to whom I had given some of the plant for the sake of the beautiful Stephonoceri which inhabited it, came in with a glass trough containing a little branch, to which adhered a dirty parchment¬ like ramifying tube, dotted here and there with brown oval masses, and having sundry open extrem¬ ities, from which some polyp-shaped animals put forth long pearly tentacles margined with vibrating cilia, and making a lively current. The creatures presented an organization higher than that of polyps, for there was an evident differentiation and com¬ plication of parts. They, therefore, belonged to the Polyzoa , or Bryozoa * a very important division
* Volyzon means “many animals,” in allusion to their habit of living in association. Bryozoa, “moss-animals,” from some having that appearance.
MARVELS OF POND-LIFE.
158
of the mull u sea. The Polyzoa are chiefly ma¬ rine, and the common "sea-mat,” often erroneously treated as a sea-weed , is a well-known form. Another species often picked up on our coasts is the Ser- tularia , or Sea- Fir, composed of delicate branching stems of a horny-looking substance, which, under a pocket-lens, is found to contain an immense number of small cells inhabited by the Polyzoa.
These animals were formerly associated with the polyps, to which they bear a strong superficial re¬ semblance; but they are of a much higher degree of organization, as will be seen by comparing what has been said in a former chapter on the Hydra , with the description which we now proceed to abridge from Dr. Allman’s splendid monograph on the fresh- water kinds In order to get a general conception of a Polyzoon, the Professor tells us to imagine an alimentary canal, consisting of oesopha¬ gus, stomach, and intestine, to be furnished at its origin with long ciliated tentacles, and to have a single nervous ganglion on one side of the oesophagus. We must then conceive the intestine bent back till its anal orifice comes near the mouth; and this curved digestive tube to be suspended in a bag con¬ taining fluid, and having two openings, one for the mouth and the other for the vent. A system of muscles enables the alimentarv tube to be retracted
%j
or protruded, the former process pulling the bag
ERRATUM.
In page 158, the Ser tularin, a compound polyp, is inadvertently spoken of as a Polyzoa , with which it should have been contrasted.
Phimatelia rcpen.3 on a leaf.
PLUMATELLA R E P E N S .
159
in, and the latter letting it out. The mouth of the bag is, so to speak, tied round the creature’s neck just below the tentacles, which are the only portions of it that are left free. The investing sack has in nearly every case the power of secreting an external sheath, more or less solid, and which branches forming numerous cells, in which the mem¬ bers of the family live in a socialistic community, having, as it were, two lives, one individual, and the other shared in common with the rest.
The whole group of tubes and cells, whatever may be the form in which they are aggregated, is called the Polypary , or, as Dr. Allman prefers, the Ccencecium , (hollow house;) the creature he names a Polypide , (polyp-like;) and the disk which bears the tentacles Lophophore , (crest-bearer.) There are some more hard words to be learnt before the student can enjoy himself scientifically among the Polyzoa, and we shall be compelled to employ some of them before we have done; but will now endeavour to describe what was presented to our view by the specimen obtained from the Hampstead Pond.
The general aspect of a branch of Plumatella repens — the creature we have to describe — is given in the drawing annexed. When all was quiet, the mouths of the bags belonging to each cell were slowlv everted, and out came a numerous bundle of tentacles, which were either spread like the corolla
160
MARVELS OF POND-LIFE.
of a fiower, or permitted to hang dishevelled like the snake-locks of Medusa. We will suppose these organs symmetrically expanded, and that we are looking down upon them with a magnifying power of sixty diameters, the light having been carefully adjusted by turning the reflecting mirror a little on one side, to avoid a direct glare. The tentacles, each of which curves with a living grace, and dis¬ plays an opaline tint in its glassy structure, do not form a complete circle, for at one place we discern two slightly diverging arms of the disk, or frame (Lophophore) from which they grow.
These arms support tentacles, on each side, and leave a gap between, so that the whole pattern is crescentic , or crescent-shaped, and not circular. Extending as far as the points of the arms, and carried all round the crescent, is an extremelv delicate membrane, like the finest gauze, which unites all the tentacles by their basal portions, and makes an elegant scallop or retreating curve between every two. Each tentacle exhibits two rows" of cilia, which scintillate as their vibrations cause them to catch the light. The motion of the cilia is in¬ variably down one side, and up the other, the current or pattern being carried on from one tentacle to the other, all through the series. This charac¬ teristic, and the facility with which each cilium can be distinguished, gives great interest and beauty
EPITOMES OF PLUMATELLA REPENS.
1()1
to the spectacle of this wonderful apparatus, by which water-currents are made to bathe the ten¬ tacles, and assist respiration, and also to carry food towards the mouth, over which a sort of finger or tongue is stretched to guard the way, and exercise some choice as to what particles shall be permitted to pass on. This organ is called the epistome , from two Greek words, signifying aupon the mouth.”
If the cell is an old one, it may be covered with so much extraneous matter as to obscure the economy within; but we are fortunate in having a transpa¬ rent specimen before us, through which we can see all that goes on. The alimentary tube, after forming a capacious cavity, much longer than it is broad, turns round and terminates in an orifice near the mouth, and just below the integuments. When refuse has to be discharged, this orifice is protruded; and after the operation is over, it draws back as before. Long muscles, composed of separate threads or fibres, pull the creature in and out of its cell, and at the part where the stomach ends, and the intestine turns round, is attached a long flexible rope, called the funiculus , which goes to the bottom of the cell. The passage of the food down to the stomach, its digestion, and the eviction of the resi¬ due, can all be watched ; and when a large morsel is swallowed, the spectacle is curious in the extreme.
One day a polypide caught a large rotifer, (K.
M
162 MARVELS OF POND-LIFE.
vulgaris ,) which, with several others of its tribe, had been walking over the ccenoecium , and swimming amongst the tentacles, as if unconscious of danger. All of a sudden it went down the whirlpool leading to the mouth, was rolled up by a process that could not be traced, and without an instant’s loss of time, was seen shooting down in rapid descent to the gulf below, where it looked a potatoe-shaped mass, utterly destitute of its characteristic living form. Having been made into a bolus, the unhappy rotifer, who never gave the faintest sign of vitality, was tossed up and down from the top to the bottom of the stomach, just as a billiard-ball might be thrown from the top to the bottom of a stocking. This process went on for hours, the ball gradually diminishing in size, until at last it was lost in the general brown mass with which the stomach was tilled. The bottom of the stomach seems well sup¬ plied with muscular fibres, to cause the constrictions by which this work is chiefiy performed, and by keeping a colony for a month or two, I had many opportunities of seeing my Polyzoa at their meals.
When alarmed the tentacles were quickly retracted, but although these creatures are said to dislike the light, and usually keep away from it in their native haunts, my specimens had no objection to come out in a strong illumination, and seemed perfectly' at their ease. They were indeed most amiable crea-
PROCESS OF GROWTH.
163
tures, and never failed to display their charms to admiring visitors, who rewarded them by unmeasured praise. Twice I had an opportunity of observing an action I cannot explain, except by supposing either that the tentacles of the Plumatella have some poison-threads like the polyps, or that rotifers are susceptible of fear. On these occasions the common rotifer was the subject of the experiment. First one, and then another got among the tentacles, and on escaping seemed very poorly. One fellow was, to borrow a phrase from Professor Thomas Sayers, “completely doubled up,” and two or three seconds— long periods in a rotifer’s life — elapsed before he came to himself again.
By keeping a colony of the Plumatella for a few weeks in a glass trough, and occasionally supplying them with fresh water from an aquarium, containing animalcules, they are easily preserved in good health, and as they develop fresh cells, the process of growth may be readily watched. This production of fresh individuals enlarges the parent colony, but could not be the means of founding a new one, which is accomplished by two other modes. A little way down the cells Professor Allman discovered an ovary attached to the internal tube by a short • peduncle , or foot-stalk, while a testis or male generative organ is attached to the funiculus , or “little rope,” we have already described.
164
MARVELS OF POND-LIFE.
July and August are the best times for observing the ovaries, and they are most conspicuous in the genera Alcyonella and Paludicella. True eggs are developed in the ovaries in a manner resembling this mode of multiplication in other animals; but there is another kind of egg, or, perhaps to speak more properly, a variety of bud, which is extremely curious. In looking at our specimens we noticed brown oval bodies in the cells; these, on careful examination, presented the appearance of the sketch. The centre is dark, covered with a net-work, which is more conspicuous in the lighter coloured and more transparent margins. These curious bodies are produced from the funiculus, and act as reserves of propagative force, as they are not hatched or
developed until they get out and find themselves
exposed to appropriate circumstances. Professor Allman names them Statoblasts , or stationary germs, and they bear some resemblance to what are called the “winter eggs” of some other creatures. The Professor was never able to discover any mode by which they were permitted to escape from the cells, and in our colonies none were allowed to leave
their homes until the death of their parent, and the decomposition of its cell had taken place; a
process which went on contemporaneously with the growth of new cells, until the plant on which the ccenoecinm was situated, rotted away, and then
TUBES OF PLUMATELLA.
165
unfortunately the whole concern went to pieces.
The tubes of the Plumatella , and of most other Polyzoa, are composed of two coats, called respec¬ tively endocyst and ectocyst , that is, “inner case” and “outer case.” The first is vitally endowed, and exhibits vessels and muscular fibres. The
second or outer case is thrown off bv the first. It
•/
is a parchment-like substance, strengthened by the adhesion of dirt particles, and does not appear to exercise any vital functions, but to be merely a covering for protection. The inner layer terminates in the neck of the bag before described, as exserted when the polypide comes out, and inverted when it goes in. This mode of making a case or sheath by inversion of a bag, is technically called inva¬ gination, and is readily seen in new and transparent cells.
The movement of eversion , or coming out, is chiefly produced by the contraction of the endocyst; while the inversion , or getting in again, is per¬ formed by the long muscles, which, when the animal is extended, are seen attached to it like ropes. Upon these muscles Professor Allman remarks that they are “especially interesting in a physiological point of view, as they seem to present us with an example of true muscular tissue, reduced to its simplest and essential form. A muscle may here be viewed as a beautiful dissection far surpassing
166
MARVELS OF POND-LIFE.
the most refined preparation of the dissecting needle, for it is composed of a bundle of elementary fibres, totally separate from one another through their entire con rse.” lie further adds, “The fibres of the great retractor muscle are distinctly marked by transverse striae ; — a condition, however, which is not at all times equally perceptible, and some of our best observers have denied to the Polyzoon the existence of striated fibre.”
We can confirm the fact of this sort of fibre being uresent, but we fancy a reader not versed in the mysteries of physiology, exclaiming, ‘What does it matter whether his fibres are striped or not?’ It does however matter a great deal ; and if Pluma- tella could hear I)r. Allman lecture upon its structure, it would be proud to find its muscles of the most tristocratic sort. Muscles in the highest animals ire composed of fasciculi, or little bundles of fibres, separated into still smaller bundles, which are again ‘parable into single or ultimate fibres, which are of two kinds. One exhibits transverse marks or strim, and the other does not. The first is the structure of muscles obedient to the will ; the last of muscles belonging to the purely organic life, over which the will has no control. The first kind of muscles are usually excited to action by nerves; the last have their contractility, which is an inherent property of muscular fibre, excited by stimuli, that
STRUCTURE OF PLUMATELLA.
1(P
act directly upon them,* and without the previous or simultaneous production of sensation or con¬ sciousness.
There are many other genera and species of fresh¬ water polyzoa besides the Plumatella repens, and they are' found attached' to sticks, stones, or leaves, generally to the under surface of the latter. They are all objects of great interest and beauty, which, whatever their diversity, conform sufficiently to one type that the student who has observed one, will easily recognise the zoological position of another. They should be viewed by transmitted and by re¬ flected light, and by dark-ground illumination, which produces very beautiful effects. To observe them in the performance of their functions, they require more room than the live-box can afford, but are well shewn in the glass trough, whose moveable diaphragm enables them to be brought near enough to the object glass, for the use of a power of about sixty linear for general purposes, and of from one to two hundred for the examination of particular parts. For a more detailed examination dissection must be employed, but all that we have mentioned can be seen without injury to the living animal, if specimens are kept till new cells are formed in water, which does not contain enough dirt to render their integuments opaque.
# Carpenter’s Manual of Physiology, p. 212.
CHAPTER XII
DECEMBER.
MICROSCOPIC HUNTING IN WINTER— WATER-BEARS, OR TARDI- GRADA— THEIR COMICAL BEHAVIOUR— MODE OF VIEWING THEM— SINGULAR GIZZARD— WENllAM’S COMPRESSORIUM — ACHROMATIC CONDENSER— MOUTH OF THE WATER-BEAR— WATER-BEARS’ EXPOSURE TO HEAT— SOLUBLE ALBUMEN — PHYSIOLOGICAL AND CHEMICAL REASONS WHY THEY ARE NOT KILLED BY HEATING AND DRYING— THE TRACHELIUS OVUM— MODE OF SWIMMING— METHOD OF VIEWING— BY DARK- GROUND ILLUMINATION— CURIOUS DIGESTIVE TUBE WITH BRANCHES— MULTIPLICATION BY DIVISION— CHANGE OF FORM IMMEDIATELY FOLLOWING THIS PROCESS — SUBSEQUENT APPEARANCES.
CHAPTER XII.
DECEMBER
There is always satisfaction in finding a work accomplished; hut the attempt to delineate some of the marvels of minute creation has been a pleasant one, and we approach the completion of our task of recording a Microscopic Year with something like regret. The dark, dirty December of the great metropolis may not seem a promising time for field excursions, but some ponds lie near enough to prac¬ ticable roads and paths to render an occasional dip in them — not of ourselves, but of our bottles — an easy and not unpleasant performance; and if the weather is unusually bad, we can fall back upon our preserves in bottles and tanks, which seldom fail to afford something new, as we have been pretty sure to bring home some undeveloped germs with our stock of pond-water and plants, and even creatures of considerable size are very likely to have escaped detection in our first efforts at examination.
When objects are not over abundant, as is apt
172
MARVELS OF POND-LIFE.
to be the case in the cold months, it is well to fill a large vial with some water out of the