Se Pi Pha ahr Bh a = ee ee ee Ana aetiettinellitidnctamage Cote Atak - . TR wT alent tte fate pb : 28 i Sia Bins ABD teen SIT pot eee a Seth aE Reem messi @ . EO Pte PN Me el i ie Ne cn BB Pla Dnt pte Rela in eI oP ilps dE waeastthorinecee Ae paiareanc’ ~ aE pine she —— A Ny STUDIES IN ANIMAL LIFE. BY GEORGE HENRY LEWES, te AUTHOR OF ‘'LIFE OF GOETHE,’ ‘‘ THE PHYSIOLOGY OF COMMON LIFE,” &e., &e. NEW YORK: HARPER & BROTHERS, PUBLISHERS, FRANKLIN SQUARE, 1860. eT Came esi CONTENTS. CHAPTER I. Omnipresence of Life.—The Microscope.—An Opalina and its Wonders.—The Uses of Cilia.—How our Lungs are protected from Dust and Filings. —Feeding without a Mouth or Stomach. —What is an Organ?—How a complex Organism arises.— Early Stages of a Frog and a Philosopher.—How the Plants feed.—Parasites of the Frog.—Metamorphoses and Migrations of Parasites.—Life within Life.—The budding of Animals.— —A steady Bore.—Philosophy of the infinitely little .....Page 9 CHAPTER II. Ponds and Rock-pools. —Our necessary Tackle.— Wimbledon Common. — Early Memories.— Gnat Larve.— Entomostraca and their Paradoxes.—Races of Animals dispensing with the sterner Sex.—Insignificance of Males. —Volvox Globator : is it an Animal ?—Plants swimming like Animals.—Animal Retro- gressions.—The Dytiscus and its Larva.—The Dragon-fly Lar- va.—Mollusks and their Eggs.—Polypes, and how to find them. —A new Polype, Hydra rubra.—Nest-building Fish.—Con- rump Temaced: Dy REVeLENCO.<.....ss..+0+,ssce casas soon cacneenmeeus 39 CHAPTER III. A garden Wall, and its Traces of past Life.—Not a Breath per- ishes.—A Bit of dry Moss and its Inhabitants. —The ‘‘ Wheel- bearers.”” — Resuscitation of Rotifers: drowned into Life.— Current Belief that Animals can be revived after complete De- siccation.—Experiments contradicting the Belief.—Spallanzani’s Testimony.—Value of Biology as a Means of Culture. —Classi- fication of Animals: the five great Types.—Criticism of Cu- ee MG METAL OINON Gems naa savidvenses te daceudeacs qavans oseeureeeeeteneen 59 vill CONTENTS. CHAPTER IV. An extinct Animal recognized by its Tooth: how came this to be possible ?—The Task of Classification.—Artificial and natural Methods.—Linnzus, and his Baptism of the Animal Kingdom: his Scheme of Classification—What is there underlying all true Classification ?—The chief Groups.—What is a Species ?— Restatement of the Question respecting the Fixity or Variability of Species.—The two Hypotheses.—I]lustration drawn from the Romance Languages.—Caution to Disputants............ Page 86 CHAPTER V. Talking in Beetles.—Identity of Egyptian Animals with those now existing: Does this prove Fixity of Species P—Examination of the celebrated Argument of Species not having altered in four thousand Years.—Impossibility of distinguishing Species from Varieties.—The Affinities of Animals.—New Facts proving the Fertility of Hybrids.—The Hare and the Rabbit contrasted.— Doubts respecting the Development Hypothesis—On Hypoth- esis in Natural History.—Pliny, and his Notion on the Forma- tion of Pearls.—Are Pearls owing to a Disease of the Oyster ?— Formation of the Shell; Origin of Pearls.—How the Chinese MAW ACtUTe! PCALIS ....2..0cccsecese se ssceceeecweeseeeaeeaeeaenes 107 CHAPTER VI. Every Organism a Colony.—What is a Paradox ?—An Organ is an independent Individual and a dependent one.—A Branch of Coral.—A Colony of Polypes.—The Siphonophora.—Uni- versal Dependence.—Youthful Aspirings.—Our Interest in the Youth of great Men.—Genius and Labor.—Cuvier’s College Life; his Appearance in Youth; his Arrival in Paris.—Cuvier and Geoffroy St. Hilaire.—Causes of Cuvier’s Success.—Qne of his early Ambitions.—M. le Baron.— Omnia vincit labor.—Con- clusion....... sedapebs sch eduectivucececaseveesnveeeseeoainansh = aammaEe 128 STUDIES IN ANIMAL LIFE. CEA iii Omnipresence of Life.-—The Microscope.—An Opalina and its Wonders.—The Uses of Cilia.—How our Lungs are protected from Dust and Filings.—Feeding without a Mouth or Stomach. —What is an Organ?—How a complex Organism arises.— Early Stages of a Frog and a Philosopher.—How the Plants feed.—Parasites of the Frog.—Metamorphoses and Migrations of Parasites.—Life within Life.—The budding of Animals.— —A steady Bore.—Philosophy of the infinitely little. CoME with me, and lovingly study Nature, as she breathes, palpitates, and works under myriad forms of Life—forms unseen, unsuspected, or unheeded by the mass of ordinary men. Our course may be through park and meadow, garden and lane, over the swelling hills and spacious heaths, beside the running and sequestered streams, along the tawny coast, out on the dark and dangerous reefs, or under dripping caves and slippery ledges. It matters lit- tle where we go: every where—in the air above, the earth beneath, and waters under the earth—we are surrounded with Life. Avert your eyes a while from our human world, with its ceaseless anxieties, its noble sorrow, poignant, yet sublime, of conscious imperfection aspiring to higher states, and contem- A 2 10 STUDIES IN ANIMAL LIFE. plate the calmer activities of that other world with which we are so mysteriously related. I hear you exclaim, ‘The proper study of mankind is man ;” nor will I pretend, as some gale Tes students seem to think, that ‘“'The proper study of mankind is cells ;”’ but agreeing with you, that man is the noblest study, I would suggest that under the noblest there are other problems which we must not neglect. Man himself is imperfectly known, because the laws of universal Life are imperfectly known. His life forms but one grand illustration of Biology—the science of Life,* as he forms but the apex of the animal world. Our studies here will be of Life, and chiefly of those minuter or obscurer forms, which seldom at- tract attention. In the air we breathe, in the water we drink, in the earth we tread on, Life is every where. Nature lives: every pore is bursting with Life; every death is only a new birth, every grave a cradle. And of this we know so little, think so little! Around us, above us, beneath us, that great mystic drama of creation is being enacted, and we will not even consent to be spectators! Unless animals are obviously useful or obviously hurtful * The needful term Biology (from Bios, life, and logos, dis- course) is now becoming generally adopted in England, as in Ger- many. It embraces all the separate sciences of Botany, Zoology, Comparative Anatomy, and Physiology. STUDIES IN ANIMAL LIFE. 11 to us, we disregard them. Yet they are not alien, but akin. The Life that stirs within us stirs with- in them. We are all “parts of one transcendent whole.” The scales fall from our eyes when we think of this; it is as if a new sense had been vouch- safed to us, and we learn to look at Nature with a more intimate and personal love. Life every where! The air is crowded with birds —heautiful, tender, intelligent birds—to whom life is a song and a thrilling anxiety, the anxiety of love. The air is swarming with insects—those lit- tle animated miracles. The waters are peopled with innumerable forms, from the animalcule, so small that one hundred and fifty millions of them would not weigh a grain, to the whale, so large that it seems an island as it sleeps upon the waves. The bed of the seas is alive with polypes, crabs, star-fishes, and with sand-numerous shell-animal- cules. The rugged face of rocks is scarred by the silent boring of soft creatures, and blackened with countless mussels, barnacles, and limpets. Life every where! on the earth, in the earth, crawling, creeping, burrowing, boring, leaping, run- ning. Ifthe sequestered coolness of the wood tempt us to saunter into its checkered shade, we are sa- luted by the murmurous din of insects, the twitter of birds, the scrambling of squirrels, the startled rush of unseen beasts, all telling how populous is this seeming solitude. If we pause before a tree, or shrub, or plant, our cursory and half-abstracted 12 STUDIES IN ANIMAL LIFE. glance detects a colony of various inhabitants. We pluck a flower, and in its bosom we see many a charming insect busy at its appointed labor. We pick up a fallen leaf, and if nothing is visible on it, there is probably the trace of an insect larva hidden in its tissue, and awaiting there development. The drop of dew upon this leaf will probably contain its. animals, visible under the microscope. This same microscope reveals that the blood-ramm sudden- ly appearing on bread, and awakening superstitious terrors, is nothing but a collection of minute ani- _ mals (Monas prodigiosa); and that the vast tracts of snow which are reddened in a single night owe their color to the marvelous rapidity in reproduc- tion of a minute plant (Protococcus nivalis). The very mould which covers our cheese, our bread, our jam, or our ink, and disfigures our damp walls, is nothing but a collection of plants. The many-col- ored fire which sparkles on the surface of a summer sea at night, as the vessel plows her way, or which drips from the oars in lines of jeweled light, is pro- duced by millions of minute animals. Nor does the vast procession end here. Our very mother-earth is formed of the débris of life. Plants and animals which have been build up its solid fabric.* We dig downward thousands of feet be- low the surface, and discover with surprise the * See Enrenpere: Microgeologie: das Erden und Felsen schaffende Wirken des unsichtbar kleinen selbststéndigen Lebens auf der Erde. 1854. STUDIES IN ANIMAL LIFE. BUS skeletons of strange, uncouth animals, which roamed the fens and struggled through the woods before man was. Our surprise is heightened when we learn that the very quarry itself is mainly com- posed of the skeletons of microscopic animals; the flints which grate beneath our carriage wheels are but the remains of countless skeletons. The Apen- nines and Cordilleras, the chalk cliffs so dear to homeward-nearing eyes—these are the pyramids of by-gone generations of atomies. Ages ago these tiny architects secreted the tiny shells which were their palaces; from the ruins of these palaces we - build our Parthenons, our St. Peters, and our Lou- vres. So revolves the luminous orb of Life! Gen- erations follow generations; and the Present be- comes the matrix of the Future, as the Past was of the Present—the Life of one epoch forming the pre- lude to a higher Life. When we have thus ranged air, earth, and water, finding every where a prodigality of living forms, visible and invisible, it might seem as if the survey were complete. And yetitis not so. Life cradles within Life. The bodies of animals are little worlds, having their own animals and plants. A celebrated Frenchman has published a thick octavo volume devoted to the classification and description of “The Plants which grow on Men and Animals;”* and many Germans have described the immense variety * CuarLes Rosin: Histoire Naturelle des Végitaux Parasites qui crosssent sur Homme et sur les Animaux Vivants. 1853. 14 STUDIES IN ANIMAL LIFE. of animals which grow on and in men and animals; so that science can now boast of a parasitic Flora and Fauna. In the fluids and tissues, in the eye, in the liver, in the stomach, in the brain, in the muscles, parasites are found, and these parasites have often ther parasites living in them! We have thus taken a bird’s-eye view of the field in which we may labor. It is truly inexhaustible. We may begin where we please, we shall never come to an end; our curiosity will never slacken. *¢ And whosoe’er in youth Has through ambition of his soul given way To such desires, and grasp’d at such delights, Shall feel congenial stirrings late and long.”’ As a beginning, get a microscope. If you can not borrow, boldly buy one. Few purchases will yield you so much pleasure; and, while you are about it, do, if possible, get a good one. Spend as little money as you can on accessory apparatus and ex- pensive fittings, but get a good stand and good glasses. Having got your instrument, bear in mind these two important trifles—work by daylight, sel- dom or never by lamplight; and keep the unoccu- pied eye open. With these precautions you may work daily for hours without serious fatigue to the eye. Now where shall we begin? Any where will do. This dead frog, for example, that has already been made the subject of experiments, and is now awaiting the removal of its spinal cord, will serve STUDIES IN ANIMAL LIFE. 15 us as a text from which profitable lessons may be drawn. We snip outa portion of its digestive tube, which, from its emptiness, seems to promise little; but a drop of the liquid we find in it is placed on a glass slide, covered with a small piece of very - thin glass, and brought under the microscope. Now look. There are several things which might occu- Mj SN Hes ty, Ya GD aD Sah gi Nes be ay Naa ao Sallie t ye Oil?» dll Ml esi gs, Ol eNite Fig. 1.—OpaALInaA RANARUM. A, front view; B, side view—mag- nified. py your attention, but dis- regard them now to watch that animalcule which you observe swimming about. Whatisit? Itis one of the largest of the Infusoria, and is named Opalina. When I call this an Infusorium I am using the language of text-books; but there seems to be a growing belief among zoologists that the Opalina is not an Infusorium, but the infantile condition of some worm (Distoma?). However, it will not grow into a mature worm as long as it inhabits the frog; it waits till some pike or bird has devoured the frog, and then, in the stomach of its new captor, it will develop into its mature form—then, and not till then. This surprises you. And well it may; but thereby hangs a tale, which to unfold—for the present, however, it must be postponed, because the Opalina itself needs all our notice. 16 STUDIES IN ANIMAL LIFE. Observe how transparent it is, and with what easy, undulating grace it swims about; yet this swimmer has no arms, no legs, no tail, no backbone to serve as a fulcrum to moving muscles—nay, it has no muscles to move with. “Tis a creature of the most absolute abnegations—sans eyes, sans teeth, sans every thing; no, not sans every thing, for, as we look attentively, we see certain currents pro- duced in the liquid, and, on applying a higher mag- nifying power, we detect how these currents are produced. All over the surface of the Opalina there are delicate hairs in incessant vibration ; these are the cilia.* They lash the water, and the animal is propelled by their strokes, as a galley by its hund- red oars. This is your first sight of that ciliary ac- tion of which you have so often read, and which you will henceforth find performing some important service in almost every animal youexamine. Some- times the cilia act as instruments of locomotion; sometimes as instruments of respiration, by contin- ually renewing the current of water; sometimes as the means of drawing in food, for which purpose they surround the mouth, and by their incessant action produce a small whirlpool into which the food is sucked. An example of this is seen in the Vorticella. (Fig. 2.) Having studied the action of these cilia in micro- scopic animals, you will be prepared to understand their office in your own organism. The lining * From cilium, a hair. STUDIES IN ANIMAL LIFE. 17 GROUP OF VORTICELLA NEBULIFERA on a Stem of Weed, magnified. A, one undergoing spontaneous division; B, another spirally retracted on its stalk; C, one with cilia rejracted; D, a bud detached and swimming free. membrane of your air-passages is covered with cilia, which may be observed by following the directions of Professor Sharpey, to whom science is indebted for a very exhaustive description of these organs. “To see them in motion, a portion of the ciliated mucous membrane may be taken from a recently- killed quadruped. The piece of membrane is to be folded with its free, or ciliated surface outward, placed on a slip of glass, with a little water or serum of blood, and covered with thin glass or mica, When it is now viewed with a power of 200 diam- 18 STUDIES IN ANIMAL LIFE. eters or upward, a very obvious agitation will be perceived on the edge of the fold, and this appear- ance is caused by the moving cilia with which the surface of the membrane is covered. Being set close together, and moving simultaneously or in -quick succession, the cilia, when in brisk action, give rise to the appearance of a bright transparent fringe along the fold of the membrane, agitated by such a rapid and incessant motion that the single threads which compose it can not be perceived. The motion here meant is that of the cilia them- selves; but they also set In motion the adjoining fluid, driving it along the ciliated surface, as is in- dicated by the agitation of any little particles that may accidentally float in it. The fact of the con- veyance of fluids and other matters along the cili- ated surface, as well as the direction in which they are impelled, may also be made manifest by im- mersing the membrane in fluid, and dropping on it some 'finely-pulverized substance (such as charcoal in fine powder), which will be slowly but steadily carried along in a constant and determinate direc- tion.”* It is an interesting fact, that while the direction in which the cilia propel fluids and particles is gen- erally toward the interior of the organism, it is sometimes reversed, and, instead of beating the par- * Quain’s Anatomy. By SHarpey and Exuis. Sixth edition. I., p. lxxiii. See also SHaRPey’s article CiZa, in the Cyclopedia of Anatomy and Physiology. STUDIES IN ANIMAL LIFE. 19 ticles inward, the cilia energetically beat them back if they attempt to enter. Fatal results would ensue if this were not so. Our air-passages would no longer protect the lungs from particles of sand, coal- dust, and filings flying about the atmosphere; on the contrary, the lashing hairs which cover the sur- face of these passages would catch up every parti- cle, and drive it onward into the lungs. Fortunate- ly for us, the direction of the cilia is reversed, and they act as vigilant janitors, driving back all va- grant particles with a stern ‘‘No admittance, even on business!” In vain does the whirlwind dash a column of dust in our faces—in vain does the air, darkened with coal-dust, impetuously rush up the nostrils; the air is allowed to pass on, but the dust is inexorably driven back. Were it not so, how could miners, millers, 1ron-workers, and all the mod- ern Tubal Cains contrive to live in their loaded ~ atmospheres? In a week their lungs would be choked up. Perhaps you will tell me that this zs the case— that manufacturers of iron and steel are very subject to consumption, and that there is a peculiar discol- oration of the lungs which has often been observed in coal-miners examined after death. Not being a physican, and not intending to trouble you with medical questions, I must still place be- fore you three considerations, which will show how untenable this notion is. First, although consump- tion may be frequent among the Sheffield workmen, 20 STUDIES IN ANIMAL LIFE. the cause is not to be sought in their breathing filings, but in the sedentary and unwholesome con- finement incidental to their occupation. Miners and coal-heavers are not troubled with consump- tion. Moreover, if the filings were the cause, all the artisans would suffer, when all breathe the same atmosphere. Secondly, while it is true that dis- colored lungs have been observed in some miners, it has not been observed in all or in many; where- as it has been observed in men not miners, not ex- posed to any unusual amount of coal-dust. Third- ly, and most conclusively, experiment has shown that the coal-dust can not penetrate to the lungs. Claude Bernard, the brilliant experimenter, tied a bladder containing a quantity of powdered char- coal to the muzzle of a rabbit. Whenever the an- imal breathed, the powder within the bladder was seen to be agitated. Hxcept during feeding-time the bladder was kept constantly on, so that the animal breathed only this dusty air. If the powder could have escaped the vigilance of the cilia and got into the lungs, this was a good occasion. But when the rabbit was killed and opened many days afterward, no powder whatever was found in the lungs or bronchial tubes; several patches were col- lected about the nostrils and throat, but the cilia had acted as a strainer, keeping all particles from the air-tubes. The swimming apparatus of the Opalina has led us far away from the little animal who has been STUDIES IN ANIMAL LIFE, Zi feeding while we have been lecturing. At the men- tion of feeding you naturally look for the food that is eaten, the mouth and stomach that eat. But I hinted just now that this ethereal creature dispenses with a stomach, as too gross for its nature, and of course, by a similar refinement, dispenses with a mouth. Indeed, it has no organs whatever except the cilia just spoken of. The same is true of several of the Infusoria, for you must know that naturalists no longer recognize the complex organization which HKhrenberg fancied he had detected in these micro- scopic beings. If it pains you to relinquish the piquant notion of a microscopic animalcule having a structure equal in complexity to that of the ele- phant, there will be ample compensation in the notion which replaces it, the notion of an ascending series of animal organisms, rising from the struc- tureless ameeba to the complex frame of a mammal. On a future occasion we shall see that, great as Khrenberg’s services have been, his znterpretations of what he saw have one by one been replaced by truer notions. His immense class of Infusoria has been, and is constantly being, diminished; many of his animals turn out to be plants; many of them embryos of worms; and some of them belong to the same divisions of the animal kingdom as the oyster and the shrimp—that is to say, they range with the Mollusks and Crustaceans. In these, of course, there is a complex organization; but in the Infusoria, as now understood, the organization is es STUDIES IN ANIMAL LIFE. extremely simple. No one now believes the clear spaces visible in their substance to be stomachs, as Khrenberg believed; and the idea of the Polygas- trica, or many-stomached Infusoria, is abandoned. No one now believes the colored specs to be eyes, because, not to mention the difficulty of conceiving eyes where there is no nervous system, it has been found that even the spores of some plants have these colored specs, and they are assuredly not eyes. If, then, we exclude the highly-organized Kotijera, or ‘‘ Wheel Animalcules,” which are genuine Crus- tacea, we may say that all Infusoria, whether they be the young of worms or not, are of very simple organization. And this leads us to consider what biologists mean by an organ: it is a particular portion of the body set apart for the performance of some particu- lar function. ‘The whole process of development is this setting apart for special purposes. The start- ing-point of Life is a single cell—that is to say, a microscopic sac, filled with liquid and granules, and having within it a nucleus, or smaller sac. Paley has somewhere remarked that in the early stages there is no difference discernible between a frog and a philosopher. It is very true—truer than he con- ceived. In the earliest stage of all, both the Ba- trachian and the Philosopher are nothing but single cells, although the one cell will develop into an Aristotle or a Newton, and the other will get no higher than the cold, damp, croaking animal which STUDIES IN ANIMAL LIFE. 23 boys will pelt, anatomists dissect, and Frenchmen eat. Hrom the starting-point of a single cell this is the course taken: the cell divides itself into two, the two become four, the four eight, and so on, till a mass of cells is formed not unlike the shape of a mulberry. This mulberry-mass then becomes a sac, with double envelopes or walls; the inner wall, turned toward the yelk, or food, becomes the assim- lating surface for the whole; the outer wall, turned toward the surrounding medium, becomes the sur- face which is to bring frog and philosopher into contact and relation with the external world—the Non-Ego, as the philosopher in after life will call it. Here we perceive the first grand “setting apart,” or differentiation, has taken place; the embryo having an assimilating surface, which has little to do with the external world, and a sensitive, contractile sur- face, which has little to do with the preparation and transport of food. ‘The embryo is no longer a mass of similar cells; it is already become dissimilar, az jerent, as respects its inner and outer envelope. But these envelopes are at present uniform; one part of each is exactly like the rest. Let us, there- fore, follow the history of Development, and we shall find that the inner wall gradually becomes un- like itself in various parts, and that certain organs, constituting a very complex apparatus of Digestion, Secretion, and Excretion, are all one by one wrought out of it by a series of metamorphoses or dfferentia- tions. The inner wall thus passes from a simple 24 STUDIES IN ANIMAL LIFE. assimilating surface to a complex apparatus serving the functions of vegetative life. Now glance at the outer wall: from it also vari- ous organs have gradually been wrought; it has de- veloped into muscles, nerves, bones, organs of sense, and brain—all these from a simple homogeneous membrane! With this bird’s-eye view of the course of devel- opment you will be able to appreciate the grand law first clearly enunciated by Goethe and Von Baer as the law of animal life, namely, that devel- opment is always from the general to the special, from the simple to the complex, from the homoge- neous to the heterogeneous, and this by a gradual series of differentiations.* Or, to put it into the music of our deeply meditative Tennyson, ‘¢ All nature widens upward. Evermore The simpler essence lower lies: More complex is more perfect—owning more Discourse, more widely wise.” You are now familiarized with the words ‘ differ- entiation” and “development,” so often met with in modern writers, and have gained a distinct idea of what an “organ” is, so that, on hearing of an animal without organs, you will at once conclude that in such an animal there has been no setting apart of any portion of the body for special pur- poses, but that all parts serve all purposes indis- * GortTHE: Zur Morphologie, 1807. Von Barr: Zur Entwick- elungsgeschichte, 1828. Part I., p. 158. ’ ee STUDIES IN ANIMAL LIFE. 25 eriminately. Here is our Opalina, for example, without mouth, or stomach, or any other organ. It is an assimilating surface in every part; in every part a breathing, sensitive surface. Living on liquid food, it does not need a mouth to seize, or a stomach to digest such food. The liquid, or gas, passes through the Opalina’s delicate skin by a process which is called endosmosis ; it there serves as food; and the refuse passes out again by a similar process, called exosmosis. This is the way in which many animals and all plants are nourished. The cell at the end of a rootlet, which the plant sends burrow- - ing through the earth, has no mouth to seize, no open pores to admit the liquid that it needs; never- theless, the liquid passes into the cell through its delicate cell-wall, and passes from this cell to other cells upward from the rootiet to the bud. It is in this way, also, that the Opalina feeds: it is all- mouth, no-mouth ; all-stomach, no-stomach. Hvery part of its body performs the functions which in more complex animals are performed by organs specially setapart. It feeds without mouth, breathes without lungs, and moves without muscles. The Opalina, as I said, is a parasite. It may be found in various animals, and almost always in the frog. You will perhaps ask why it should be con- sidered a parasite? why may it not have been swal- lowed by the frog in a gulp of water? Certainly nothing would have been easier. But, to remove your doubts, I open the skull of this frog, and care- B 26. STUDIES IN ANIMAL LIFE. fully remove a drop of the liquid found inside, which, on being brought under a microscope, we shall most probably find containing some animal- cules, especially those named MJonads. ‘These were not swallowed. They live in the cerebro-spinal fluid, as the Opalina lives in the digestive tube. Nay, if we extend our researches, we shall find that various organs have their various parasites. Here, for instance, is a parasitic worm from the frog’s bladder. Place it under the microscope with a high power, and behold! It is called Polystomum— many-mouthed, or, more properly, many-suckered. You are looking at the un- der side, and will observe six large suckers with their starlike clasps (e), and the a. horny instrument (/) with a ) e which the animal bores its Was way. Ata there is anoth- ye ( . — (Oe er sucker, which serves Y@ S&S also as a mouth; at 6 you Fig. ee eeRGEEEE: perceive the rudiment of a gullet, and at d the repro- ductive organs. But pay attention to the pretty | branchings of the digestive tube (c), which ramifies through the body like a blood-vessel. This arrangement of the digestive tube is found —=>= —S=S> Sass > & SN Nps Okan ZA = ———=—_=>_= BE zs aS—= ! AS STUDIES IN ANIMAL LIFE. PAT in many animals, and is often mistaken for a system of blood-vessels. In one sense this is correct, for these branching tubes are carriers of WES and but the nutriment is chyme, not nce ie lube SS animals have not arrived at thé dignity of.blood, | which is a higher elaboration of the food, fitted for higher organisms. Thus may our frog, besides its ae Smaihe af ea ford us many “ authentic tidings of invisible things,” and is itself a little colony of life. Nature is eco- nomic as well as prodigal of space. She fills the il- limitable heavens with planetary and starry grand- eurs, and the tiny atoms moving over the crust of earth she makes the homes of the infinitely little. Far as the mightiest telescope can reach, it detects worlds in clusters, like pebbles on the shore of in- finitude; deep as the microscope can penetrate, it detects life within hfe, generation within genera- tion, as if the very universe itself were not vast enough for the energies of life! - That phrase, generation within generation, was not a careless phrase; it is exact. Take the tiny insect (Aphis) which, with its companions, crowds your rose-tree; open it, in a solution of sugar-water, under your microscope, and you will find in it a young insect nearly formed; open that young in- sect with care, and you will find in it, also, another young one, less advanced in its development, but _ perfectly recognizable to the experienced eye; and 28 STUDIES IN ANIMAL LIFE. beside this embryo you will find many eggs, which would in time become insects! Or take that lazy water-snail (Paludina vivipara), first made known to science by the great Swam- merdamm, the incarnation of patience and exact- ness, and you will find, as he found, forty or fifty young snails in various stages of development; and you will also find, as he found, some tiny worms, which, if you cut them open, will suffer three or four infusoria to escape from the opening.* In your astonishment you will ask, Where is this to end? The observation recorded by Swammerdamm, like so many others of this noble worker, fell into neglect, but modern investigators have made it the starting-point of a very curiousinquiry. The worms he found within the snail are now called Cercaria sacs, because they contain the Cercarie, once classed as Infusoria, and which are now known to be the early forms of parasitic worms inhabiting the di- gestive tube and other cavities of higher animals. These Cercarie have vigorous tails, with which they swim through the water like tadpoles, and, like tad- poles, they lose their tails in after life. But how, think you, did these sacs containing Cercarie get into the water-snails? ‘By spontaneous genera- tion,” formerly said the upholders of that hypothe- sis, and those who condemned the hypothesis were forced to admit they had no better explanation. It was a mystery which they preferred leaving unex- * SwamMMERDAMM. Bibel der Natur, p. 75-77. STUDIES IN ANIMAL LIFE. 29 plained rather than fly to spontaneous generation. And they were right. The mystery has at length been cleared up.* I will endeavor to bring togeth- er the scattered details, and narrate the curious story. Under the eyelids of geese and ducks may be constantly found a parasitic worm (of the Trematode order), which naturalists have christened Monosto- mum mutabile—Single-mouth, Changeable. This worm brings forth living young, in the likeness of active Infusoria, which, being covered with cilia, swim about in the water as we saw the Opalina swim. Here is a portrait of one. A B ZZ ris Fig. 4.-A, Empryo or Monostomum MUTABILE. B, Cercaria sac, just set free. ad, mouth; b, pigment spots; c, sac—magnified. Hach of these animalcules develops a sac in its interior. ‘The sac you may notice in the engraving. * By Von SrezBotp. See his interesting work, Ueber die Band- und-Blasenwiirmer. It has been translated by Huxiey, and ap- pended to the translation of KUECHENMEISTER on Parasites, pub- lished by the Sydenham Society. 30 STUDIES IN ANIMAL LIFE. Having managed to get into the body of the water- snail, the animalcule’s part in the drama is at an end. It dies, and in dying liberates the sac, which is very comfortably housed and fed by the snail. If you examine this sac (Fig. 5), you will observe that it has a mouth and digestive tube, and is, therefore, very far from being, what its name imports, a mere receptacle; it is an independent animal, and lives an Sze” =independent life. It feeds generously Fig. 5.—CERCARIA etre : : f Sac. on the juices of the snail, and, having A th; B, di- . . Zestive tube; c, fed, thinks generously of the coming a cercaria newly formed: fouroth- generations. It was born inside the different stages animalcule; why shouldit not in turn i ae give birth to children of its own? To found a dynasty, to scatter progeny over the boun- teous earth, is a worthy ambition. The mysterious agency of reproduction begins in this sac-animal, and in a short while a brood of Cercarice move within it. The sac bursts, and the brood escapes. But how is this? The children are by no means the “ very image” of their parent. They are not sacs, nor in the least resembling sacs, as Fig. 6.—CERCARIA DEVEL- you see (Fig. 6). OPED. A, mouth; B, B, B, excre- They have tails, and suckers tory organ; C, pigment ; spots; D, tail. and sharp boring instruments, STUDIES IN ANIMAL LIFE, Ay with other organs which their parent was without. To look at them you would as soon suspect a shrimp to be the progeny of an oyster, as these to be the progeny of the sac-animal. And what makes the paradox more paradoxical is, that not only are the Cercarie unlike their parent, but their parent was equally unlike its parent, the embryo of Menosto- mum (compare Fig. 4). However, if we pursue this family history, we shall find the genealogy rights itself at last, and that this Cercaria will develop in the body of some bird into a Monostomum mutabile like its ancestor. ‘Thus the worm produces an an- imalcule, which produces a sac-animal, which pro- duces a Cercaria, which becomes a worm exactly resembling its great-grandfather. One peculiarity in this history is, that while the Monostomum produces its young in the usual way, the two intermediate forms are produced by a process of budding analogous to that observed in plants. Plants, as you know, are reproduced in two ways —from the seed and from the bud. For seed- reproduction peculiar organs are necessary; for bud-reproduction there is no such differentiation needed: it is simply an outgrowth. The same is true of many animals; they also bud like plants, and produce seeds (eggs) like plants. I have else- where argued that the two processes are essentially identical, and that both are but special forms of erowth.* Not, however, to discuss so abstruse a * Seaside Studies, p. 308 et sq. 32 STUDIES IN ANIMAL LIFE. question here, let us merely note that the Monosto- mum, into which the Cercaria will develop, produces egos, from which young will issue; the second gen- eration is not produced from eggs, but by internal budding; the third generation is likewise budded internally, but it, on acquiring maturity, will pro- duce eggs. For this maturity, it is indispensable that the Cercaria should be swallowed by some bird or animal; only in the digestive tube can it acquire its producing condition. How is it to get there? The ways are many; let us witness one: In this watch-glass of water we have several Cer- carve Swimming about. To them we add three or four of those darting, twittering insects which you have seen in every vase of pond-water, and have learned to be the larve or early forms of the EHphemeron. The Cercarie cease flapping the water with their impatient tails, and commence a severe scrutiny of the strangers. When Odry, in the riot- ous farce Les Saltembanques, finds a portmanteau, he exclaims, ‘Un malle! ce dowt étre d mor!” (“Surely this must belong to me!”) ‘This seems to be the theory of property adopted by the Cercaria: ‘‘ An insect! surely this belongs to me!” Accordingly every one begins creeping over the bodies of the Ephemera, giving an interrogatory poke with the spine, which will pierce the first soft place it can detect. Between the segments of the insect’s armor a soft and pierceable spot is found; and now, lads, to work! Onward they bore, never relaxing in Nag? STUDIES IN ANIMAL LIFE. oo their efforts ull a hole is made large enough for them to slip in by elongating their bodies. Once in, they dismiss their tails as useless appendages, and begin what is called the process of encysting— that is, of rolling themselves up into a ball, and se- creting a mucus from their surface which hardens round them likeashell. Thus they remain snugly ensconced in the body of the insect, which in time develops into a fly, hovers over the pond, and is swallowed by some bird. The fly is digested, and the liberated Cercaria finds itself in comfortable quarters, its shell is broken, and its progress to ma- turity is rapid. Von Siebold’s description of another form of em- igration he has observed in parasites will be read with interest. ‘For a long time,” he says, “the origin of the thread-worm, known as [lara insec- torum, that lives in the cavity of the bodies of adult and larval insects, could not be accounted for. Shut up within the abdominal cavity of caterpillars, grass- hoppers, beetles, and other insects, these parasites were supposed to originate by spontaneous genera- tion under the influence of wet weather or from de- cayed food. Helminthologists (students of parasitic worms) were obliged to content themselves with this explanation, since they were unable to find a better. Those who dissected these thread-worms, and submitted them to a careful inspection, could not deny the probability, since it was clear that they contained no trace of sexual organs. But, on di- B2 34 STUDIES IN ANIMAL LIFE. recting my attention to these entozoa, I became aware of the fact that they were not true filarve at all, but belonged to a peculiar family of thread- worms, embracing the genera of Gordius and Mer- mis. Furthermore, I convinced myself that these parasites wander away when full grown, boring their way from within through any soft place in the body of their host, and creeping out through the opening. These parasites do not emigrate be- cause they are uneasy, or because the caterpillar is sickly, but from that same internal necessity which constrains the horsefly to leave the stomach of the horse where he has been reared, or which moves the gadfly to work its way out through the skin of the ox. The larvee of both these insects creep forth in order to become chrysalises, and thence to pro- ceed to their higher and perfect condition. I have demonstrated that the perfect, full-grown, but sex- less thread-worms of insects are in like manner moved by their desire to wander out of their pre- vious homes in order to enter upon a new period of their lives, which ends in the development of their sex. As they leave the bodies of their hosts, they fall to the ground and crawl away into the deeper and moister parts of the soil. Thread- worms found in the damp earth, in digging up gar- dens and cutting ditches, have often been brought to me which presented no external distinctions from the thread-worms of insects. This suggested to me that the wandering thread-worms of insects might STUDIES IN ANIMAL LIFR. 385 instinctively bury themselves in damp ground, and I therefore instituted a series of experiments by placing the newly-emigrated worms in flower-pots filled with damp earth. To my delight, I soon per- ceived that they began to bore with their heads into the earth, and by degrees drew themselves entirely in. Hor many months I kept the earth in the flow- er-pots moderately moist, and, on examining the worms from time to time, I found they had gradu- ally attained their sex-development, and eggs were deposited in hundreds. ‘Toward the conclusion of winter I could succeed in detecting the commencing development of the embryos in these eggs. By the end of spring they were fully formed, and many of them, having left their shells, were to be seen creep- ing about the earth. I now conjectured that these young worms would be impelled by their instincts to pursue a parasitic existence, and to seek out an animal to inhabit and to grow to maturity in; and it seemed not improbable that the brood I had reared would, like their parents, thrive best in the caterpillar. In order, therefore, to induce my young brood to immigrate, I procured a number of very small caterpillars, which the first spring sunshine had just called into life. For the purpose of my experiment, I filled a watch-glass with damp earth, taking it from among the flower-pots where the thread-worms had wintered. Upon this I placed several of the young caterpillars.” The result was as he expected; the caterpillars were soon bored 36 STUDIES IN ANIMAL LIFE. into by the worms, and served them at once as food and home.” Frogs and parasites, worms and infusoria—are these worth the attention of a serious man? They have a less imposing appearance than planets and asteroids I admit, but they are nearer to us, and ad- mit of being more intimately known, and, because they are thus accessible, they become more import- ant to us. The life that stirs within us is also the life within them. It is for this reason, as I said at the outset, that, although man’s noblest study must always be man, there are other studies less noble, yet not therefore ignoble, which must be pursued, even if only with a view to the perfection of the noblest. Many men, and these not always the ig- norant, whose scorn of what they do not under- stand is always ready, despise the labors which do not obviously and directly tend to moral or political advancement. Others there are who, fascinated by the grandeur of Astronomy and Geology, or by the immediate practical results of Physics and Chem- istry, disregard all microscopic research as little bet- ter than dilettante curiosity. But I can not think any serious study is without its serious value to the human race; and I know that the great problem of Life can never be solved while we are in igno- | rance of its simpler forms. Nor can any thing be more unwise than the attempt to limit the sphere —_ * Von SrespoLtp: Ueber Band-und-Blasenwiirmer. ‘Translated by Hux er. STUDIES IN ANIMAL LIFE. 37 of human inquiry, especially by applying the test of immediate utility. All truths are related; and, however remote from our daily needs some partic- ular truth may seem, the time will surely come when its value will be felt. To the majority of our countrymen during the Revolution, when the con- duct of James seemed of incalculable importance, there would have seemed something ludicrously ab- surd in the assertion that the newly-discovered dif- ferential calculus was infinitely more important to Hngland and to Europe than the fate of all the dy- nasties; and few things could have seemed more remote from any useful end than this product of mathematical genius; yet it is now clear to every one that the conduct of James was supremely insig- nificant in comparison with this discovery. I do not say that men were unwise to throw themselves body and soul into the Revolution ; I only say they would have been unwise to condemn the researches of mathematicians. Let all who have a longing to study Nature in any of her manifold aspects do so without regard to the sneers or objections of men whose tastes and faculties are directed elsewhere. From the illumi- nation of many minds on many points Truth must finally emerge. Man is, in Bacon’s noble phrase, the minister and interpreter of Nature; let him be careful lest he suffer this ministry to sink into a priesthood, and this interpretation to degenerate into an immovable dogma. The suggestions of 38 STUDIES IN ANIMAL LIFE. apathy and the prejudices of ignorance have at all times inspired the wish to close the temple against new comers. Let us be vigilant against such sug- gestions, and keep the door of the temple ever open. a STUDIES IN ANIMAL LIFE. 0. CHAPTER II. Ponds and Rock-pools. —Our necessary Tackle.— Wimbledon Common. — Early Memories.— Gnat Larve.— Entomostraca and their Paradoxes.—Races of Animals dispensing with the sterner Sex.—lInsignificance of Males.—Volvox Globator: is it an Animal ?—Plants swimming like Animals.—Animal Retro- gressions.—The Dytiscus and its Larva.—The Dragon-fly Lar- va.—Mollusks and their Eggs.—Polypes, and how to find them. —A new Polype, Hydra rubra.—Nest-building Fish.—Con- tempt replaced by Reverence. THE day is bright with a late autumn sun; the sky is clear with a keen autumn wind, which lashes our blood into a canter as we press against it, and the cantering blood sets the thoughts into hurrying excitement. Wimbledon Common is not far off; its five thousand acres of undulating heather, furze, and fern tempt us across it, health streaming in at every step as we snuff the keen breeze. We are tempted also to bring net and wide-mouthed jar, to ransack its many ponds for visible and invisible wonders. Ponds, indeed, are not so rich and lovely as rock- pools; the heath is less alluring than the coast— our dear-loved coast, with its gleaming mystery, the sea, and its sweeps of sand, its reefs, its dripping boulders. I admit the comparative inferiority of ponds, but, you see, we are not near the coast, and AQe STUDIES IN ANIMAL LIFE. the heath is close at hand. Nay, if the case were otherwise, I should object to dwarfing comparisons. It argues a pitiful thinness of nature (and the major- ity in this respect are lean) when present excellence is depreciated because some greater excellence is to” be found elsewhere. We are not elsewhere; we must do the best we can with what is here. Be- cause ours is not the Klizabethan age, shall we ex- press no reverence for our great men, but reserve it for Shakspeare, Bacon, and Raleigh, whose tra- ditional renown must overshadow our contempo- raries? Not so. To each age its honor. Let us be thankful for all greatness, past or present, and never speak slightingly of noble work or honest endeavor because it is not, or we choose to say it is not, equal to something else. No comparisons, then, IT beg. IfI said ponds were finer than rock-pools, you might demur; but I only say ponds are excel- lent things, let us dabble in them; ponds are rich in wonders, let us enjoy them. And, first, we must look to our tackle. It is ex- tremely simple. A landing-net, lined with muslin; a wide-mouthed glass jar, say a foot high and six inches in diameter, but the size optional, with a bit of string tied under the lip, and forming a loop over the top, to serve as a handle, which will let the jar swing without spilling the water; a camel’s-hair brush; a quinine bottle, or any wide-mouthed phi- al, for worms and tiny animals which you desire to keep separated from the dangers and confusions of s STUDIES IN ANIMAL LIFE. 41 the larger jar; and when to these a pocket lens is added, our equipment is complete. As we emerge upon the common and tread its springy heather, what a wild wind dashes the hair into our eyes, and the blood into our cheeks! and what a fine sweep of horizon lies before us! The lingering splendors and the beautiful decays of au- tumn vary the scene, and touch it with a certain pensive charm. ‘The ferns mingle harmoniously their rich browns with the dark green of the furze, now robbed of its golden summer glory, but still pleasant to the eye and exquisite to memory. The gaunt wind-mill on the rising ground is stretching its stiff, starred arms into the silent air, a land- mark for the wanderer—a land-mark, too, for the wandering mind, since it serves to recall the dim early feelings and sweet broken associations of a childhood when we gazed at it with awe, and listen- ed to the rushing of its mighty arms. Ah! well may the mind with the sweet insistance of sadness linger on those scenes of the irrecoverable past, and try, by lingering there, to feel that it is not wholly lost, wholly irrecoverable, vanished forever from the Life which, as these decays of autumn and these changing trees too feelingly remind us, is gliding away, leaving our cherished ambitions still unful- filled, and our deeper affections still but half ex- pressed. The vanishing visions of elapsing life bring with them thoughts which lie too deep for tears, and this wind-mill recalls such visions by A2 STUDIES IN ANIMAL LIFE. the subtle laws of association. Let us go toward it, and stand once more under its shadow. See the in- telligent and tailless sheep-dog which bounds out at our approach, eager and minatory; now his quick eye at once recognizes that we are neither tramps nor thieves, and he ceases barking to commence a lively interchange of sniffs and amenities with our Pug, who seems also glad of a passing interchange of commonplace remarks. While these dogs travel over each other’s minds, let us sun ourselves upon this bench, and look down on the embrowned val- ley, with its gipsy encampment, or abroad on the purple Surrey hills, or the varied-tinted trees of Combe Wood and Richmond Park. There are not many such prospects so near London. But, mm spite of the sun, we must not linger here: the wind is much too analytical in its remarks; and, more- over, we came out to hunt. Here is a pond with a mantling surface of green promise. Dip the jar into the water. Hold it now up to the light, and you will see an immense varie- ty of tiny animals swimming about. Some are large enough to be recognized at once; others re- quire a pocket lens, unless familiarity has already enabled you to znfer the forms you can not distinct- ly see. Here (Fig. 7) are two larvee (or grubs) of the common gnat. That large-headed fellow (A) bobbing about with such grotesque movements is very near the last stage of his metamorphosis, and to-morrow, or the next day, you may see him Fig. 7, LARV OF THE GNAT in two different stages of development (magnified). cast aside this mask (/arva means a mask), and emerge a perfect insect. The other (B) is in a much less matured condition, but leads an active predatory life, jerking through the water, and fast- ening to the stems of weed or sides of the jar by means of the tiny hooks at the end ofits tail’ > Pine hairy appendage forming the angle is not another tail, but a breathing apparatus. Observe, also, those grotesque Entomostraca,* popularly called ““water-fleas,” although, as you perceive, they have little resemblance in form or manners to our familiar (somewhat é00 familiar) bed-fellows. This (Fig. 8) is a Cyclops, with only one eye in the centre of its forehead, and carrying two sacs, filled with eggs, like panniers. You ob- * Entomostraca (from entomos, an insect, and ostracon, a shell) are not really insects, but belong to the same large group of ani- mals as the lobster, the crab, or the shrimp—. e., crustaceans. 44 STUDIES IN ANIMAL LIFE. serve he has no legs; or, rather, legs and arms are Fig. 8.—CYcLors. Fig. 9. DAPHNIA. a, large antenns; 0b, smaller do. ; a, pulsatile sac, or heart; b, eggs; c, egg-sacs (magnified). ce, digestive tube (magnified). hoisted up to the head, and become antennz (or feelers). Here (Fig. 9) is a Daphnia, grotesque enough, throwing up his arms in astonished awk- wardness, and keeping his legs actively at work inside the shell—as res- pirators, in fact. Here (Fig. 10) is a Hurycer- cus, less grotesque, and with a much smaller eye. Talking of eyes, there is one of these Hntomos- traca, named Polyphemus, whose head is all eye; and another, named Caliqus, who has no head at all. Other paradoxes and wonders are presented by this interesting group of animals;* but they all sink A] wee Fig. 10.—EvURYcCERCUS. a, heart; b, eggs; c, digestive tube (magnified). * The student will find ample information in Barrp’s British Entomostraca, published by the Ray Society. STUDIES IN ANIMAL LIFE. 45 into insignificance beside the paradox of the ama- zonian entomostracon, the Apus—a race which dis- penses with masculine services altogether, a race of which there are no males! I well remember the pleasant evening on which I first made the personal acquaintance of this ama- zon. It was at Munich, and in the house of a cele- brated naturalist, in whose garden an agreeable as- semblage of poets, professors, and their wives saun- tered in the light of a setting sun, breaking up into groups and ¢ées-d-tétes, to re-form into larger groups. We had taken coffee under the branching coolness of trees, and were now loitering through the brief interval till supper. Our host had just returned from an expedition of some fifty miles to a particu- lar pond, known to be inhabited by the Apus. He had made this journey because the race, although prolific, is rare, and is not to be found in every spot. For three successsive years had he gone to the same pond in quest of the male; but no male was to be found among thousands of egg-bearing females, some of which he had brought away with him, and was showing us. We were amused to see them Swimming about, sometimes on their backs, using their long oars, sometimes floating, but always in- cessantly agitating the water with their ten. pairs of breathing legs; and the ladies, gathered round the jar, were hugely elated at the idea of animals getting rid altogether of the sterner sex—clearly a useless encumbrance in the scheme of things! 46 STUDIES IN ANIMAL LIFE. — The fact that no male Apus has yet been found is not without precedent. Léon Dufour, the cele- brated entomologist, declares that he never found the male of the gall insect (Diplolepis galle tunctorie), though he has examined thousands: they were all females, and bore well-developed eggs on emerging from the gall-nut in which their infancy had pass- ed. In two other species of gall insect—Cynips di- visa and OCynips folui—Hartig says he was unable to find a male; and he examined about thirteen thou- sand. Brongniart never found the male of another entomostracon (Limnadia gigas), nor could Jurine find that of our Polyphemus. These negatives prove, at least, that if the males exist at all, they must be excessively rare, and their services can be dispensed with; a conclusion which becomes accept- able when we learn that bees, plant-lice (Aphides), and our grotesque friend Daphnia (Fig. 9) lay eggs which may be reared apart, will develop into fe- males, and these will produce eggs which will in turn produce other females, and so on, generation after generation, although each animal be reared in a vessel apart from all others. While on this subject, I can not forbear making a reflection. It must be confessed that our sex cuts but a poor figure in some great families. If the. male is in some families grander, fiercer, more splen- did, and more highly endowed than the female, this occasional superiority is more than counterbalanced by the still greater inferiority of the sex in other a ca ey STUDIES IN ANIMAL LIFE. 47 families. The male is often but a contemptible partner, puny in size, insignificant in powers, stint- ed even of a due allowance of organs. Ifthe pea- cock and the pheasant swagger in greater splendor, what a pitiful creature is the male falcon !—no fal- coner will look at him. And what is the drone compared with the queen bee, or even with the workers? What figure does the male spider make beside his large and irascible female, who not un- frequently eats him? Nay, worse than this, what - can be said for the male Rotifer, the male Barnacle, the male Lernzea—gentlemen who can not even boast of a perfect digestive apparatus, sometimes not of a digestive organ at all? Nor is this mea- ereness confined to the digestive system only. In some cases, as in some male Rotifers, the usual or- gans of sense and locomotion are wanting ;* and in a parasitic Lernea, the degradation is moral as well as physical: the female lives in the gills of a fish, sucking its juices, and the ignoble husband lives as a parasite upon her! But this digression is becoming humiliating, and meanwhile our hands are getting benumbed with cold. In spite of that, I hold the jar up to the light, and make a background of my forefingers, to throw into relief some of the transparent animals. Look at those green crystal spheres sailing along * Compare GrcEnBauR: Grundziige der vergleichende Anato- mie, 1859, p. 229 und 269; also Luypia iiber Hydatina senta, in Miuller’s Archiv, 1857, p. 411. 48 STUDIES IN ANIMAL LIFE. Ss Sa S40 PIV Wee th GON Se Se ! RA se i : Us BEM OAR SERS ZX REX PD Th Mo RZ AAAK BNA 4 ava fl HHI 7, A s&s s ES KOS Ui 7 WP POC fA ase ss 7 DIS Lace TEST LEI. OM Vee . ATTRA SOS SEL W\ (iii } | Fig. 11.—Votvox GLoBAToR, with eight volvoces inclosed (magnified). with slow revolving motion, like planets revolving through space, except that their orbits are more ec- centric. Hach of these spheres is a Volvox globator. Under the microscope it looks like a crystalline sphere, studded with bright green specks, from each of which arise two cilia (hairs), serving as oars to row the animal through the water. The specks are united by a delicate net-work, which is not always visible, however. Inside this sphere is a fluid, in which several dark green smaller spheres are seen revolving, as the parent sphere revolved in the wa- ter. Press this Volvox gently under your com- pressorium, or between the two pieces of glass, and you will see these internal spheres, when duly mag- nified, disclose themselves as identical with their parent; and inside them smaller Volvoces are seen. ‘T'his is one of the many illustrations of life within life, of which something was said in the last chapter. STUDIES IN ANIMAL LIFE. 49 Nor is this all. Those bright green specks which stud the surface, if examined with high powers, will turn out to be, not specks, but animals,* and, as Eh- renberg believes (though the belief is but little shared), highly organized animals, possessing a mouth, many stomachs, and an eye. It is right to add that not only are microscopists at variance with Ehrenberg on the supposed organization of these specks, but the majority deny that the Volvox itself is an animal. Von Siebold in Germany, and Pro- fessor George Busk and Professor Williamson in England, have argued with so much force against the animal nature of the Volvox, which they call a plant, that in most modern works you will find this opinion adopted. But the latest of the eminent au- thorities on the subject of Infusoria, in his magnifi- cent work just published, returns to the old idea that the Volvox is an animal after all, although of very simple organization.t The dispute may perhaps excite your surprise. You are perplexed at the idea of a plant (if plant it be) moving about, swimming with all the vigor and dexterity of an animal, and swimming by means of animal organs, the cilia. But this difficulty is one of our own creation. We first employ the word * To avoid the equivoque of calling the parts of an animal, which are capable of independent existence, by the same term as the whole mass, we may adopt HuxLEy’s suggestion, and call all such individual parts zooids instead of animals. Ducks suggested zoonites in the same sense.—Sur la Conformité Organique, p. 13. + Stein: Der Organismus der Infusionsthiere, 1859, p. 36-38. C Boe! STUDIES IN ANIMAL LIFE. plant to designate a vast group of objects which have no powers of locomotion, and then ask, with triumph, How can a plant move? But we have only to enlarge our knowledge of plant-life to see that locomotion is not absolutely excluded from it; for many of the simpler plants—Conferve and A1- ge—can and do move spontaneously in the early stages of their existence: they escape from their parents as free swimming rovers, and do not settle into solid and sober respectability till later in life. In their roving condition they are called, improper- ly enough, ‘‘ zoospores,”* and once gave rise to the opinion that they were animals in infancy, and be- came degraded into plants as their growth went on. But locomotion is no true mark of animal-nature, neither is fixture to one spot the true mark of plant- nature. Many animals (Polypes, Polyzoa, Barna- cles, Mussels, etc.), after passing a vagabond youth, “settle” once and forever in maturer age, and then become as fixed as plants. Nay, human animals not unfrequently exhibit a somewhat similar me- tempsychosis, and make up for the fitful capricious- ness of wandering youth by the steady severity of their application to business when width of waist- coat and smoothness of cranium suggest a sense of their responsibilities. Whether this loss of locomotion is to be regard- ed as a retrogression on the part of the plant or animal which becomes fixed, may be questioned; * Zoospores, from zoon, an animal, and sporos, a seed. STUDIES IN ANIMAL LIFE. 51 but there are curious indications of positive retro- eression from a higher standard in the metamor- phoses of some animals. Thus the beautiful marine worm Terebella, which secretes a tube for itself, and lives in it, fixed to the rock or oyster-shell, has in early life a distinct head, eyes, and feelers; but in growing to maturity it loses all trace of head, eyes, and even of feelers, unless the beautiful tuft of streaming threads which it waves in the water be considered as replacing the feelers. There are the Barnacles, too, which in the first stage of their ex- istence have three pairs of legs, a very simple single eye, and a mouth furnished with a proboscis. In the second stage they have six pairs of legs, two compound eyes complex in structure, two feelers, but no mouth. In the third, or final stage, their legs are transformed into prehensile organs, they have recovered a mouth, but have lost their feelers, and their two complex eyes are degraded to a single and very simple eye-spot. But, to break up these digressions, let us try a sweep with our net. Weskim it along the surface, and draw up a quantity of duckweed, dead leaves, bits of stick, and masses of green thread of great fineness, called Conferva by botanists. The water runs away, and we turn over the mass. Here is a fine water-beetle, called the ‘‘ Water-tiger,” from its ferocity (Fig. 12). You would hardly suspect that the slim, big-headed, long-tailed Water-tiger would srow into the squat, small-headed, tailless beetle ; - 52 STUDIES IN ANIMAL LIFE. Fig. 12.—WaATER BEETLE and its larva. nor would you imagine that this Water-tiger would ,. be so “high fantas- '))/ tical” as to breathe by his tail. Yet he does both, as you will find if you watch him in your aqua- rium. Continuing our search, we light up- on the fat, sluggish, ungraceful larva of the graceful and bril- liant Dragon-fly, the falcon of insects (Fig. 13). He is useful _} for dissection, so pop Fig. 13.—DBAGON-FLY Larv#: him in. Among the A, ordinary aspect; B, with the huge nipper- - "like jaw extended. dead leaves you per- STUDIES IN ANIMAL LIFE. 53 ceive several small leeches, and flat oval Plana- rice, white and brown; and here also is a jelly- like mass, of pale yellow color, which we know to be a mass of eggs deposited by some shell- fish; and, as there are few objects of greater inter- est than an egg in course of development, we pop the mass in. Here (lig. 14) are two mollusks, Lum- Fig. 14,—A, Limn2us STAGNALIS, or Water-snail. B, PLANORBIS., neus and Planorbis, one of which is probably the parent of those eggs. And here is one which lays no eggs, but brings forth its young alive: it is the Paludina vivipara (Fig. 15), of which we learned some interest- in 2 details last month. Fig. 15,—PALupIna VIVIPARA. 54 STUDIES IN ANIMAL LIFE. Scattered over the surface of the net and dead leaves are little dabs of dirty-looking jelly—some of them, instead of the dirty hue, are almost blood-red. Ex- perience makes me aware that these dirty dabs are certainly Polypes—the Hydra fusca of systematists. I can’t tell how it is I know them, nor how you may know them again. The power of recognition must be acquired by familiarity; and it is because men can’t begin with familiarity, and can’t recognize these Polypes without it, that so few persons really ever see them. But the familiarity may be acquired by a very simple method. Make it a rule to pop every unknown object into your wide-mouthed phial. In the water it will probably at once reveal its nature: if it be a Polype, it will expand its tentacles; if not, you can identify it at leisure on reaching home by the aid of pictures and descriptions. See, as I drop one of these into the water, it at once assumes the well- known shape of the Polype. And now we will see what these blood-red dabs may be; in spite of their unusual color, I can not help suspecting them to be Polypes also. Give me the camel-hair brush. Gen- tly the dab is removed, and transferred to the phial. Shade of Trembley! it 2s a Polype!* Is it possible that this discovery leaves you imperturbable, even * TREMBLEY, in his admirable work, Mémoires pour servir a Vhistoire d’une genre de Polypes d’eau douce, 1744, furnished science with the fullest and most accurate account of fresh-water Polypes; but it is a mistake to suppose that he was the original discoverer of this genus: old LeEvwENHOEK had been before him. STUDIES IN ANIMAL LIFE. 55 when I assure you it is of a species hitherto unde- scribed in text-books? Now don’t be provokingly indifferent! rouse yourself to a little enthusiasm, and prove that you have something of the natural- ist in you by delighting in the detection of a new species. ‘You didn’t know that it was new?” That explains your calmness. There must be a basis of knowledge before wonder can be felt— wonder being, as Bacon says, ‘“ broken knowledge.” _ Learn, then, that hitherto only three species of fresh-water Polypes have been described: Hydra viridis, Hydra fusca, and Hydra grisea. We have now a fourth to swell the list; we will christen it Alydra rubra, and be as modest in our glory as we ean. Ifany one puts it to us whether we seriously attach importance to such trivialities as specific dis- tinctions resting solely upon color or size, we can look profound, you know, and repudiate the charge. But this is a public and official attitude. In pri- vate we can despise the distinctions established by others, but keep a corner of favoritism for our own.* I remember once showing a bottle containing Polypes to a philosopher, who beheld them with great calmness. They appeared to him as insignifi- * The editors of the Annals of Natural History append a note to the account I sent them of this new Polype, from which it appears that Dr. Gray found this very species, and apparently in the same spot, nearly thirty years ago. But the latest work of authority, VAN DER Hoven’s Handbook of Zoology, only enumerates the three species. 56 STUDIES IN ANIMAL LIFE. cant as so many stems of duckweed; and, lest you should be equally indifferent, I will at once inform you that these creatures will interest you as much as any that can be found in ponds, if you take the trouble of studying them. They can be cut into many pieces, and each piece will grow into a per- fect Polype; they may be pricked or irritated, and the irritated spot will bud a young Polype, as a plant buds; they may be turned inside out, and their skin will become a stomach, their stomach a skin. They have acute sensibility to ight (toward which they always move), and to the slightest touch; yet not a trace of a nervous tissue is to be found in them. They have powers of motion and locomo- tion, yet their muscles are simply a network of large contractile cells. If the water in which they are kept be not very pure, they will be found in- fested with parasites; and quite recently I have no- ticed an animal or vegetal parasite—I know not which—forming an elegant sort of fringe to the tentacles; clusters of skittle-shaped bodies, too en- tirely transparent for any structure whatever to be made out, in active agitation, like leaves fluttering on atwig. Some day or other we may have occa- sion to treat of the Polypes in detail, and to narrate | the amusing story of their discovery; but what has already been said will serve to sharpen your atten- tion, and awaken some curiosity in them. Again and again the net sweeps among the weed or dredges the bottom of the pond, bringing up mud, STUDIES IN ANIMAL LIFE. 57 stones, sticks, with a fish, worms, mollusks, and tri- tons. The fish we must secure, for it is a stickle- back—a pretty and interesting inhabitant of an aquarium, on account of its nest-building propensi- ties. We are surprised at a fish building a nest and caring for its young like the tenderest of birds (and there are two other fishes, the Goramy and the Hassar, which have this instinct); but why not a fish as well as a bird? ‘The catfish swims about in company with her young, like a proud hen with her chickens, and the sunfish hovers for weeks over her eggs, protecting them against danger. The wind is so piercing, and my fingers are so benumbed, I can scarcely hold the brush. More- over, continual stooping over the net makes the muscles ache unpleasantly, and suggests that each east shall be the final one. But somehow I have made this resolution and broken it twenty times: either the cast has been unsuccessful, and one is provoked to try again, or it is so successful that, as Pappétt vient en mangeant, one is seduced again. Very unintelligible this would be to the passers- by, who generally cast contemptuous glances at us when they find we are not fishing, but are only re- moving nothings into a glass jar. One day an Trish laborer stopped and asked me if I were fish- ing for salmon. I quietly answered “Yes.” He drew near. I continued turning over the weed, oc- casionally dropping an invisible thing into the wa- ter. At last a large yellow-bellied Triton was C 2 58 STUDIES IN ANIMAL LIFE. dropped in. He begged to see it; and, seeing at the same time how alive the water was with tiny animals, became curious, and asked many questions. I went on with my work; his interest and curiosity increased ; his questions multiplied; he volunteered assistance; and remained beside me till I prepared to go away, when he said seriously, ‘Och! then, and it’s a fine thing to be able to name all God’s creatures.” Contempt had given place to rever- ence; and so it would be with others, could they check the first rising of scorn at what they do not understand, and patiently learn what even a road- side pond has of Nature’s wonders. STUDIES IN ANIMAL LIFE. 59 CHAPTER III. A garden Wall, and its Traces of past Life.—Not a Breath per- ishes.—A Bit of dry Moss and its Inhabitants. —The ‘‘ Wheel- bearers.” — Resuscitation of Rotifers: drowned into Life.— Current Belief that Animals can be revived after complete De- siccation.—Experiments contradicting the Belief.—Spallanzani’s Testimony.—Value of Biology as a Means of Culture.—Classi- fication of Animals: the five great Types.—Criticism of Cu- vier’s Arrangement. PLEASANT, both to eye and mind, is an old gar- den wall, dark with age, gray with lichens, green with mosses of beautiful hues and fairy elegance of form; a wall shutting in some sequestered home, far from “the din of murmurous cities vast;” a home where, as we fondly, foolishly think, Life must needs throb placidly, and all its tragedies and pettinesses be unknown. As we pass alongside this wall, the sight of the overhanging branches sug- gests an image of some charming nook; or our thoughts wander about the wall itself, calling up the years during which it has been warmed by the sun, chilled by the night airs and the dews, and dashed against by the wild winds of March, all of which have made it quite another wall from what it was when the trowel first settled its bricks. The old wall has a past, a life, a story; as Wordsworth 60 STUDIES IN ANIMAL LIFE. finely says of the mountain, it is “ familiar with for- gotten years.” Not only are there obvious traces of age in the crumbling mortar and the battered brick, but there are traces, not obvious except to the inner eye, left by every ray of light, every rain- drop, every gust. Nothing perishes. In the won- drous. metamorphosis momently going on every where in the universe, there is change, but no loss. Lest you should imagine this to be poetry, and not science, I will touch on the evidence that every beam of light, or every breath of air which falls upon an object, permanently affects it. In photog- raphy we see the effect of light very strikingly ex- hibited; but perhaps you will object that this proves nothing more than that light acts upon an iodized surface. Yet, in truth, light acts upon, and more or less alters the structure of every object on which it falls. Nor is this all. Ifa wafer be laid on a sur- face of polished metal, which is then breathed upon, and if, when the moisture of the breath has evapo- rated, the wafer be shaken off, we shall find that the whole polished surface is not as it was before, al- though our senses can detect no difference; for if we breathe again upon it, the surface will be moist every where except on the spot previously shelter- ed by the wafer, which will now appear as a spec- tral image on the surface. Again and again we breathe, and the moisture evaporates, but still the spectral wafer reappears. This experiment suc- ceeds after a lapse of many months if the metal be STUDIES IN ANIMAL LIFE. 61 carefully put aside where its surface can not be dis- turbed. If a sheet of paper on which a key has been laid be exposed for some minutes to the sun- shine, and then instantaneously viewed in the dark, the key being removed, a fading spectre of the key will be visible. Let this paper be put aside for many months where nothing can disturb it, and then in darkness be laid on a plate of hot metal, the spectre of the key will again appear. In the ease of bodies more highly phosphorescent than paper, the spectres of many different objects which may have been laid on in succession will, on warm- ing, emerge in their proper order.* This is equally true of our bodies and our minds. We are involved in the universal metamorphosis. Nothing leaves us wholly as it found us. Every man we meet, every book we read, every picture or landscape we see, every word or tone we hear, mingles with our being and modifies it. There are cases on record of ignorant women, in states of in- sanity, uttering Greek and Hebrew phrases, which in past years they had heard their. masters utter, without, of course, comprehending them. These tones had: long been forgotten; the traces were so faint that under ordinary conditions they were in- visible; but the traces were there, and in the in- tense light of cerebral excitement they started into prominence, just as the spectral image of the key started into sight on the application of heat. It is * Draper: Human Physiology, p. 288. 62 STUDIES IN ANIMAL LIFE. thus with all the influences to which we are sub- jected. | If a garden wall can lead our vagabond thoughts into such speculations as these, surely it may also furnish us with matter for our Studies in Animal Life. Those patches of moss must be colonies, Suppose we examine them. I pull away a small bit, which is so dry that the dust crumbles at a touch; this may be wrapped in a piece of paper— dirt and all—and carried home. Get the micro- scope ready, and now attend. T moisten a fragment of this moss with distilled water. Any water will do as well, but the use of distilled water prevents your supposing that the animals you are about to watch were brought in it, and were not already in the moss. I now squeeze the bit between my fingers, and a drop of the con- tained water—somewhat turbid with dirt—falls on the glass slide, which we may now put on the mi- croscope stage. A rapid survey assures us that there is no animal visible. The moss is squeezed again, and this time little yellowish bodies of an irregular oval are noticeable among the particles ’ of dust and moss. Watch one of these, and pres- ently you will observe a slow bulging at one end, and then a bulging at the other end. The oval has elongated itself into a form not unlike that of a fat caterpillar, except that there is a tapering at one end. Nowa forked tail is visible; this fixes on to the glass, while the body swings to and fro. STUDIES IN ANIMAL LIFE. 63 Now the head is drawn in—as if it were swallowed —and suddenly in its place are unfolded two broad membranes, having each a circle of waving cilia. The lifeless oval has become a living animal! You have assisted at a resuscitation, not from death by drowning, but by drying: the animal has been drowned into life! The unfolded membranes, with their cilia, have so much the appearance of wheels that the name of ‘ Wheel-bearer” (fotfera) or “Wheel Animalcule” has been given to the animal. é kl [eam (Haid a? afi \\ “p (\ S) | P3 Fig. 16.—Rovirer VULGARIS. A, with the wheels drawn in (at ¢).. B, with the wheels expanded; b, eye spots; é, jaw and teeth; f, alimentary canal; g, embryo; h, embryo further developed; 7, water-vascular system; k, vent. 64. STUDIES IN ANIMAL LIFE. The Rotifera (also, and more correctly, called Fotatoria) form an interesting study. Let us glance at their organization : There are many different kinds of Rotifers, vary- ing very materially in size and shape, the males, as was stated in the last chapter, being more imper- fectly organized than the females. They may be seen either swimming rapidly through the water by means of the vibratile cilia called ‘‘ wheels,” be- cause the optical effect is very much that of a toothed wheel, or crawling along the side of the glass, fastening to it by the head, and then curving the body till the tail is brought up to the spot, which is then fastened on by the tail, and the head is set free. They may also be seen fastened to a weed, or the glass, by the tail, the body waving to and fro, or thrusting itself straight out, and setting the wheels in active motion. In this attitude the aspect of the jaws is very striking. Leuwenhoek mistook it for the pulsation of a heart, which its in- cessant rhythm much resembles. The tail and the upper part of the body have a singular power of being drawn out or drawn in, like the tube of a telescope. ‘There is sometimes a shell or carapace, but often the body is covered only with a smooth firm skin, which, however, presents decided indica- tions of being segmented. The first person who described these Rotifers was the excellent old Leuwenhoek,* and his animals * LEUWENHOEK: Select Works, ii., p. 210. His figures, how- ever, are very incorrect. STUDIES IN ANIMAL LIFE. 65 were got from the gutter of a house-top. Since then they have been minutely studied, and have been shown to be, not Infusoria, as Hhrenberg im- agined, but Crustacea.* Your attention is request- ed to the one point which has most contributed to the celebrity of these creatures—their power of re- suscitation. Leuwenhoek described —what you have just witnessed, namely—the slow resuscitation of the animal (which seemed as dry as dust, and might have been blown about like any particle of dust) directly a little moisture was brought to it. Spallanzani startled the world with the announce- ment that this process of drying and moistening— of killing and reviving—could be repeated fifteen times in succession; so that the Rotifer, whose nat- ural term of life is about eighteen days, might, it was said, be dried and kept for years, and at any time revived by moisture. ‘T'hat which seems now no better than a grain of dust will suddenly awaken to the energetic life of a complex organism, and may again be made as dust by the evaporation of the water. This is very marvelous; so marvelous that a mind trained in the cultivated caution of science will demand the evidence on which it is based. Two months ago I should have dismissed the doubt with the assurance that the evidence was ample and * See Leypic: Ueber den Bau und die systematische Stellung der Raderthiere, in StrBoLD und KoLuiKer’s Zeitschrift, vi., and Ueber Hydatina Senta, in MuLuER’s Archiv, 1857. 66 STUDIES IN ANIMAL LIFE. rigorous, and the fact indisputable; for not only had the fact been confirmed by the united experi- ence of several investigators, it had stood the test of very severe experiment. Thus, in 1842, M. Do- yére published experiments which seemed to place it beyond skepticism. Under the air-pump he set some moss, together with vessels containing sul- phuric acid, which would absorb every trace of moisture. After leaving the moss thus for a week, © he removed it into an oven, the temperature of which was raised to 800° Fahrenheit. Yet even this treat- ment did not prevent the animals from resuscitating when water was added. In presence of testimony like this, doubt will seem next to impossible. Nevertheless, my own experi- ments leave me no choice but to doubt. Not hay- ing witnessed M. Doyére’s experiment, 1 am not prepared to say wherein its fallacy lies; but that there as a fallacy seems to me capable of decisive proof. In M. Pouchet’s recent work* I first read a distinct denial of the pretended resuscitation of the Rotifers; this denial was the more startling to me, because I had myself often witnessed the reawaken- ing of these dried animals. Nevertheless, wheney- er a doubt is fairly started, we have not done jus- tice to it until we have brought it to the test of ex- periment; accordingly, I tested this, and quickly came upon what seems to me the source of the gen- * Poucnet: Hétérogénie, ou Traité de la Génération Spontanee, 1859, p. 453. STUDIES IN ANIMAL LIFE. O7 eral misconception. Day after day experiments were repeated, varied, and controlled, and with re- sults so unvarying that hesitation vanished; and as some of these experiments are of extreme simplici- ty, you may verify what I say with little trouble. Squeeze a drop from the moss, taking care that there is scarcely any dirt in it; and, having ascer- tained that it contains Rotifers or Tardigrades,* alive and moving, place the glass slide under a bell- glass, to shield it from currents of air, and there al- low the water to evaporate slowly, but completely, by means of chloride of calcium or sulphuric acid placed under the bell-glass; or, what is still sim- pler, place a slide with the live animals on the man- telpiece when a fire is burning in the grate. Ifon the day following you examine this perfectly dry glass, you will see the contracted bodies of the Ro- tifers, presenting the aspect of yellowish oval bodies; but attempt to resuscitate them by the addition of a little fresh water, and you will find that they do not revive, as they revived when dried in the moss; they sometimes swell a little, and elongate them- selves, and you imagine this is a commencement of resuscitation; but continue watching for two or three days, and you will find it goes no further. * The Tardigrade, or microscopic Sloth, belongs to the order of Arachnida, and is occasionally found in moss, stagnant ponds, ete. I have only met with four specimens in all my investigations, and they were all found in moss. SPALLANZANI described and figured it (very badly), and M. Doyre has given a fuller description in the Annales des Sciences, 2d series, vols. xiv., xvii., and xviii. 68 STUDIES IN ANIMAL LIFE. Never do these oval bodies become active crawling Rotifers; never do they expand their wheels, and set the cesophagus at work. No; the Rotifer once dried is dead, and dead forever. But if, like a cautious experimenter, you vary and control the experiment, and beside the glass slide place a watch-glass containing Rotifers with dirt or moss, you will find that the addition of wa- ter to the contents of the watch-glass will often (not always) revive the animals. What you can not ef fect on a glass slide without dirt, or with very little, you easily effect in a watch-glass with dirt or moss; and if you give due attention you will find that in each case the result depends upon the quantity of the dirt. And this leads to a clear understanding of the whole mystery ; this reconciles the conflict- ing statements. ‘The reason why Rotifers ever re- vive is because they have not been drzed—they have not lost by evaporation that small quantity of water which forms an integral constituent of their tissues ; and it is the presence of dirt or moss which prevents this complete evaporation. No one, I sup- pose, believes that the Rotifer actually revives after once being dead. If it has a power of remaining in a state of suspended animation, like that of a frozen frog, it can do so only on the condition that its or- gansm is not destroyed; and destroyed it would be if the water were removed from its tissues; for, strange as it may seem, water is not an accessory, but a constituent element of every tissue; and this STUDIES IN ANIMAL LIFE. 69 ean not be replaced mechanically—it can only be replaced by vital processes. Every one who has made microscopic preparations must be aware that when once a tissue is desiccated, it is spoiled; it will not recover its form and properties on the ap- plication of water, because the water was not orig- inally worked into the web by a mere process of imbibition—like water in a sponge—but by a molec- ular process of assimilation, like albumen in a mus- cle. Therefore I say that desiccation is necessarily death, and the Rotifer which revives can not have been desiccated. This being granted, we have only to ask, What prevents the Rotifer from becoming completely dried? Experiment shows that it is the presence of dirt or moss which does this. The whole marvel of the Rotifer’s resuscitation, there- fore, amounts to this: that if the water in which it lives be evaporated, the animal passes into a state of suspended animation, and remains so as long as its own water is protected from evaporation. Tam aware that this is not easily to be reconciled with M. Doyére’s experiment, since the application of a temperature so high as 300° Fahrenheit (nearly a hundred degrees above boiling water) must, one would imagine, have completely desiccated the ani- mals, in spite of any amount of protecting dirt. It is possible that M. Doyére may have mistaken that previously-noticed swelling up of the bodies, on the application of water, for a return to vital activity. Tf not, I am at-a loss to explain the contradiction ; 70 STUDIES IN ANIMAL LIFE. for certainly in my experience a much more mod- erate desiccation—namely, that obtained by simple evaporation over a mantelpiece or under a large bell-glass—always destroyed the animals if little or no dirt were present. The subject has recently been brought before the French Academy of Sciences by M. Davaine, whose experiments* lead him to the conclusion that those Rotifers which habitually live in ponds will not re- vive after desiccation, whereas those which live in moss always do so. I believe the explanation to be this: the Rotifers living in ponds are dried without any protecting dirt or moss, and that is the reason they do not revive. After having satisfied myself on this point, I did what perhaps would have saved me some trouble if thought of before. I took down Spallanzani, and read his account of his celebrated experiments. To my surprise and satisfaction, it appeared that he had accurately observed the same facts, but curious- ly missed their real significance. Nothing can be plainer than the following passage: ‘“ But there is one condition indispensable to the resurrection of wheel-animals: it is absolutely necessary that there should be a certain quantity of sand; without it they will not revive: One day I had two wheel- animals traversing a drop of water about to evapo- rate which contained very little sand. Three quar- ters of an hour after evaporation they were dry and * DAVAINE in Annales des Sciences Naturelles, 1858, x., p. 335. STUDIES IN ANIMAL LIFE. 71 motionless. I moistened them with water to revive them, but in vain, notwithstanding that they were immersed in water many hours. Their members swelled to thrice the original size, but they remain- ed motionless. To ascertain whether the fact was accidental, I spread a portion of sand, containing animals, on a glass slide, and waited until it became dry in order to wet it anew. The sand was care- lessly scattered on the glass, so as to be a thin coy- ering on some parts, and on others in a very small quantity: here the animals did not revive; but all that were in those parts with abundance of sand re- vived.”* He further says that if sand be spread out in considerable quantities in some places, much less in others, and very little in the rest, on moist- ening it the revived animals will be numerous in the first, less numerous in the second, and none at all in the third. | It is not a little remarkable that observations so precise as these should have for many years passed unregarded, and not led to the true explanation of the mystery. Perhaps an inherent love of the mar- velous made men greedily accept the idea of resus- citation, and indisposed them to attempt an expla- nation of it. Spallanzani’s own attempt is certainly not felicitous. He supposes that the dust prevents the lacerating influence of the air from irritating and injuring the animals. And this explanation is ac- cepted by his translator. * SPALLANZANI: Tracts on the Natural History of Animals and Vegetables: translated by Dalyell, ii., p. 129. Fe? STUDIES IN ANIMAL LIFE. [Since the foregoing remarks were in type, M. Gavarret has published (Annales des Sciences Natu- relles, 1859, x1., p. 815) the account of his experi- ments on Rotifers and Tardigrades, in which he found that after subjecting the moss to a desiccation the most complete according to our present means, the animals revived after twenty-four hours’ immer- sion of the moss in water. This result seems flatly to contradict the result I arrived at, but only seems to contradict it, for in my experiments the animals, not the moss, were subjected to desiccation. Nev- ertheless, I confess that my confidence was shaken by experiments so precise, and performed by so dis- tinguished an investigator, and I once more resumed the experiments, feeling persuaded that the detec- tion of the fallacy, wherever it might be, would be well worth the trouble. The results of these con- trolling experiments are all I can find room for here: Whenever the animals were completely separated from the dirt, they perished ; in two cases there was a very little dirt—a mere film, so to speak—in the watch-glass and glass cell, and this, slight as it was, sufficed to protect two out of eight, and three out of ten Rotifers, which revived on the second day; the others did not revive even on the third day aft- er their immersion. In one instance, a thin cover- ing-glass was placed over the water on the slide, and the evaporation of the water seemed complete, yet this glass cover sufficed to protect a Rotifer, which revived in three hours. ee a ee | STUDIES IN ANIMAL LIFE. (es If we compare these results with those obtained by M. Davaine, we can scarcely avoid the conclusion that it is only when the desiccation of the Rotifers is prevented by the presence of a small quantity of moss or of dirt—between the particles of which they find shelter—that they revive on the application of water. And even in the severe experiments of M. Doyére and M. Gavarret, some of the animals must have been thus protected; and I call particular at- tention to the fact that, although some animals re- vived, others always perished. But if the organiza- tion of the Rotifer or Tardigrade is such that it can withstand desiccation—if it only needs the fresh ap- plication of moisture to restore its activity—all, or almost all the animals experimented on ought to revive; and the fact that only some revive leads us to suspect that these have not been desiccated—a suspicion which is warranted by direct experiments. I believe, then, that the discrepancy amounts to this: investigators who have desiccated the moss’ containing animals find some of the animals revive on the application of moisture, but those who desic- cate the animals themselves will find no instances of revival. | The time spent on these Rotifers will not have been misspent if it has taught us the necessity of caution in all experimental inquiries. Although experiment is valuable—nay, indispensable—as a means of interrogating Nature, it is constantly lia- ble to mislead us into the idea that we have rightly D 14 STUDIES IN ANIMAL LIFE. interrogated and rightly imterpreted the replies; and this danger arises from the complexity of the cases with which we are dealing, and our proneness to overlook or disregard some seemingly trifling condition—a trifle which may turn out of the ut- most importance. The one reason why the study of science is valuable as a means of culture, over and above its own immediate objects, is that in it the mind learns to submit to realities instead of thrusting its figments in the place of realities—en- deavors to ascertain accurately what the order of Nature zs, and not what it ought to be or might be. The one reason why, of all sciences, Biology is pre- eminent as a means of culture, is, that, owing to the ereat complexity of all the cases it investigates, it . familiarizes the mind with the necessity of attend- ing to all the conditions, and it thus keeps the mind alert. It cultivates caution, which, considering the tendency there is in men to “ anticipate Nature,” is a mental tonic of inestimable worth. Iam far from asserting that biologists are more accurate reasoners than other men; indeed, the mass of crude hypoth- esis which passes unchallenged by them is against such an idea. But, whether its advantage be used or neglected, the truth nevertheless is, that Biology, from the complexity of its problems, and the ne- cessity of incessant verification of its details, offers creater advantages for culture than any other branch of science. T have once or twice mentioned the words Mol- STUDIES IN ANIMAL LIFE. 15 lusk and Crustacean, to which the reader unfamiliar with the language of Natural History will have at- tached but vague ideas; and although I wanted to explain these, and convey a distinct conception of the general facts of classification, 1 would have been too great an interruption. So I will here make an opportunity, and finish the chapter with an indication of the five types, or plans of struct- ure, under one of which every animal is classed. Without being versed in science, you discern at once whether the book before you is mathematical, physical, chemical, botanical, or physiological. In lke manner, without being versed in Natural His- tory, you ought to know whether the animal be- fore you belongs to the Vertebrata, Mollusca, Artic- ulata, Radiata, or Protozoa. A glance at the contents of our glass vases will yield us samples of each of these five divisions of the animal kingdom. We begin with this Triton (Fig. 17). Itis a representative of the VERTEBRATE division or sub-kingdom. You have merely to re- member that it possesses a backbone and an inter- nal skeleton, and you will at once recognize the cardinal character which makes this Triton range under the same general head as men, elephants, _ whales, birds, reptiles, or fishes. All these, in spite of their manifold differences, have this one charac- ter in common—they are all backboned; they have all an internal skeleton; they are all formed ac- cording to one general type. In all vertebrate ani- 76 STUDIES IN ANIMAL LIFE. Fig. 17.—Ma.e TRITON, OR WATER-NEWT. mals the skeleton is found to be identical in plan. Every bone in the body of a triton has its corre- sponding bone in the body of a man or of a mouse; and every bone preserves the same connection with other bones, no matter how unlike may be the va- rious limbs in which we detect its presence. Thus, widely as the arm of a man differs from the fin of a whale, or the wing of a bird, or the wing of a bat, or the leg of a horse, the same number of bones, and the same connections of the bones, are found in each. A fin is one modified form of the typical limb; an arm is another; a wing another. That which is true of the limbs is also true of all the other organs; and it is on this ground that we speak of the vertebrate type. From fish to man STUDIES IN ANIMAL LIFE. fut one common plan of structure prevails, and the presence of a backbone is the index by which to recognize this plan. The Triton has been wriggling grotesquely in our grasp while we have made him our text, and, now he is restored to his. vase, plunges to the bot- tom with great satisfaction at his escape. ‘T'his wa- ter-snail, crawling slowly up the side of the vase, and cleaning it of the green growth of microscopic plants, which he devours, shall be our representa- tive of the second great division—the MOLLUSCA. I can not suggest any obvious character so distinct- ive as a backbone by which the word mollusk may at once call up an idea of the type which prevails in the group. It won’t do to say “shellfish,” be- cause many mollusks have no shells, and many ani- mals which have shells are not mollusks. The name was originally bestowed on account of the softness of the animals. But they are not softer than worms, and much less so than jellyfish. You may know that snails and slugs, oysters and cuttle- fish, are mollusks; but if you want some one char- acter by which the type may be remembered, you must fix on the imperfect symmetry of the mol- lusk’s organs. I say cmperfect symmetry, because it is an error, though a common one, to speak of the mollusk’s body not being belateral—that is to say, of its not being composed of two symmetrical halves. A vertebrate animal may be divided lengthwise, and each half will closely resemble the other; the i 18 STUDIES IN ANIMAL LIFE. backbone forms, as it were, an axis, on either side of which the organs are disposed; but the mollusk is said to have no such axis, no such symmetry. I admit the absence of an axis, but I deny the total absence of symmetry. Many of its organs are as symmetrical as those of a vertebrate animal—. e., the eyes, the feelers, the jaws—and the gills in Cut- tlefish, Holids, and Pteropods; while, on the other hand, several organs in the vertebrate animal are as unsymmetrical as any of those in the mollusk—~. e., the liver, spleen, pancreas, stomach, and intestines.* As regards bilateral structure, therefore, it is only a question of degree. The vertebrate animal is not entirely symmetrical, nor is the mollusk entirely unsymmetrical. But there is a characteristic dis- position of the nervous system peculiar to mol- lusks: it neither forms an ais for the body, as it does in the Vertebrata and Articulata, nor a centre, as it does in the Radiata, but is altogether irregular and unsymmetrical. ‘This will be intelligible from the following diagram of the nervous systems of a mollusk and an insect, with which that of a starfish may be compared (Fig. 18). Here you perceive how the nervous centres and the nerves which * In some cases of monstrosity these organs are transposed, the liver being on the left, and the pancreas on the right side. It was in allusion to a case of this kind, then occupying the attention of Paris, that Motizre made his Medecin malgré Lui describe the heart as on the right side, the liver on the left; on the mistake be- ing noticed, he replies, ‘‘ Out, autrefois; mais nous avons changé tout cela.” STUDIES IN ANIMAL LIFE. 79 x ¥ v0) jos \ ~ ) WW eo BY 4r SS 2 a wey j ae by AR All same =e } pa xq be act SIE be Fo > lI bo 2S Git x @eo~\ CSQ lt Ox; LON ae ~O = es. CO = Be. ZoX = It ean ae I AD. PAS EN l Jb Fig. 18.—Nrrvous System OF SHA-HARE (A) and CENTIPEDE (B). Fig. 19.—NERVOUS SYSTEM OF STARFISH. 80 STUDIES IN ANIMAL LIFE. issue from them are irregularly disposed in the mollusks, and symmetrically in the insect. But the recognition of a mollusk will be easier when you have learned to distinguish it from one of the ARTICULATA, forming the third great divi- sion—the third animal type. Of these, our vases present numerous representatives—prawns, beetles, water-spiders, insect-larvee, entomostraca, and worms. There is a very obvious character by which these may be recognized: they have all bodies composed of numerous segments, and their limbs are jointed, — and they have mostly an external skeleton from which their limbs are developed. Sometimes the segments of their bodies are numerous, as in the centipede, lobster, etc.; sometimes several segments are fused together, as in the crab; and sometimes, as in worms, they are indicated by slight markings or depressions of the skin, which give the appear- ance of little rings, and hence the worms have been named Annelida, or Annulata, or Annulosa. In these last-named cases the segmental nature of the type is detected in the fact that the worms grow, segment by segment; and also by the fact that in most of them each segment has its own nerves, heart, stom- ach, etc.—each segment is, in fact, a zdoid.* Just as we recognize a vertebrate by the presence of a backbone and internal skeleton, we recognize an articulate by its jointed body and external skele- ton. In both, the nervous system forms the axis * The term zooid was explained in our last chapter. STUDIES IN ANIMAL LIFES. 81 of the body. The Mollusk, on the contrary, has no skeleton, internal or external,* and its nervous sys- tem does not form an axis. As a rule, both verte- brates and articulates have limbs, although there — are exceptions in serpents, fishes, and worms. The Mollusks have no limbs. Backboned, jointed, and non-jointed, therefore, are the three leading charac- teristics of the three types. Let us now glance at the fourth division me RADIATA, so called because of the disposition of the organs round a centre, which is the mouth. Our fresh-water vases afford us only one representative of this type—the Hydra, or fresh-water Polype, whose capture was recorded in the last chapter. Is it not strange that while all the Radiata are aquatic, not a single terrestrial representative having been discovered, only one should be found in fresh wa- ter? Think of the richness of the seas, with their hosts of Polypes, Actinise, Jellyfish, Starfishes, Sea- urchins, Sea-pens (Pennatule), Lily-stars (Comatu- dee), and Sea-cucumbers (Holothurice), and then com- pare the poverty of rivers, lakes, and ponds, re- duced to their single representative, the Hydra. The radiate structure may best be exhibited by the diagram of the nervous system of the Starfish} on page 79. * In the cuttlefish there is the commencement of an internal skeleton in the cartilage-plates protecting the brain. + It is right to add that there are serious doubts entertained re- specting the claim of a starfish to the possession of a nervous sys- D2 a 82 STUDIES IN ANIMAL LIFE. Cuvier, to whom we owe this classification of the animal kingdom into four great divisions, would have been the first to recognize the chaotic con- dition in which he left this last division, and would have acquiesced in the separation of the PROTOZOA, which has since been made. This fifth division in- cludes many of the microscopic animals known as Infusoria, and receives its name from the idea that these simplest of all animals represent, as it were, the beginnings of life.* But Cuvier’s arrangement is open to a more se- rious objection. The state of science in his day excused the imperfection of classing the Infusoria and parasites under the Radiata; but it was owing, I conceive, to an unphilosophical view of morphology that he placed the mollusks next to the Vertebrata, instead of placing the Articulata in that position. He was secretly determined by the desire to show that there are four very distinct types, or plans of structure, which can not by any transitions be brought under one law of development. Lamarck and Geoffroy St. Hilaire maintained the idea of uni- ty of composition throughout the animal kingdom: in other words, that all the varieties of animal forms were produced by successive modifications; and several of the German naturalists maintained that the vertebrata in their embryonic stages passed tem at all; but the radiate structure is represented in the diagram, as it also is, very clearly, in a Sea-anemone. * Protozoa, from proton, first, and zoon, animal. STUDIES IN ANIMAL LIFE. 83 through forms which were permanent in the lower animals. This idea Cuvier always opposed. He held that the four types were altogether distinct; and by his arrangement of them, their distinctness certainly appears much greater than would be the case on another arrangement. But, without dis- cussing this question here, it is enough to point out the fact of the enormous superiority in intelligence, in sociality, and in complexity of animal ftmctions which insects and spiders exhibit when compared with the highest of the mollusks, to justify the re- moval of the mollusca, and the elevation of the ar- ticulata to the second place in the animal hierarchy. Nor is this all. If we divide animals into four eroups, these four naturally dispose themselves into two larger groups: the first of these, comprising Vertebrata and Articulata, is characterized by a nervous axis and a skeleton; the second, comprising Mollusca and Radiata, is characterized by the ab- sence of both nervous axis and skeleton. It is ob- vious that a bee much more closely resembles a bird than any mollusk resembles any vertebrate. If there are many and important differences be- tween the vertebrate and articulate types, there are also many and important resemblances; if the nerv- ous axis is above the viscera, and forms the dorsal line of the vertebrate, whereas it is wnderneath the viscera, and forms the ventral line in the articulate, it is, nevertheless, in both, the axis of the body, and in both it sends off nerves to supply symmetrical ' 84 STUDIES IN ANIMAL LIFE. limbs; in both it has similar functions. And while the articulata thus approach in structure the verte- brate type, the mollusca are not only removed from that type by many diversities, but a number of them have such affinities with the Radiate type that it is only in quite recent days that the whole class of Polyzoa (or Bryozoa, as they are also called) has been removed from the Radiata, and ranged under the Mollusca. To quit this topic, and recur once more to the five divisions, we have only the broad outlines of the picture in Vertebrata, Mollusca, Articulata, Ra- diata, and Protozoa; but this is a good beginning, and we can now proceed to the further subdivisions. Hach of these five sub-kingdoms is divided into classes; these, again, into orders; these into fami- lies; these into genera; these into species; and these, finally, into varieties. Thus, suppose a dwarf terrier is presented to us with a request that we should indicate its various titles in the scheme of classification: we begin by calling it a vertebrate; we proceed to assign its class as the mammalian; its order is obviously that of the carnivora; its family is that of the fox, wolf, jackal, etc., named Canide ; its genus is, of course, that of Canis ; its species, terrier; its variety, dwarf terrier. Inas- much as all these denominations are the expres- sions of scientific research, and not at all arbitrary or fanciful, they imply an immense amount of labor and sagacity in their establishment; and when we STUDIES IN ANIMAL LIFE. 85 remember that naturalists have thus classed upward of half a million of distinct species, it becomes an interesting inquiry, What has been the guiding principle of this successful labor? on what basis is so large a superstructure raised? ‘This question we shall answer in the next chapter. 86 STUDIES IN ANIMAL LIFE. CHAPTER IV. An extinct Animal recognized by its Tooth: how came this to be possible ?—The Task of Classification.—Artificial and natural Methods.—Linnzus, and his Baptism of the Animal Kingdom: his Scheme of Classification—What is there underlying all true Classification ?—The chief Groups.—What is a Species ?— Restatement of the Question respecting the Fixity or Variability of Species. —The two Hypotheses.—Illustration drawn from the Romance Languages.—Caution to Disputants. I wAs one day talking with Professor Owen in the Hunterian Museum, when a gentleman approached with a request to be informed respecting the nature of a curious fossil which had been dug up by one of his workmen. As he drew the fossil from a small bag, and was about to hand it for examina- tion, Owen quietly remarked, ‘That is the third molar of the under jaw of an extinct species of rhi- noceros.” The astonishment of the gentleman at this precise and confident description of the fossil, before even it had quitted his hands, was doubtless very great. I know that mine was, until the reflec- tion occurred that if some one, little acquainted with editions, had drawn a volume from his pocket, de- claring he had found it in an old chest, any biblio- phile would have been able to say at a glance, “That is an Elzevir;” or, “That is one of the Tauchnitz classics, stereotyped at Leipzig.” Owen is as familiar with the aspect of the teeth of ani- STUDIES IN ANIMAL LIFE. 87 mals, ivymg and extinct, as a student is with the as- pect of editions. Yet, before that knowledge could have been acquired, before he could say thus confi- dently that the tooth belonged to an extinct species of rhinoceros, the united labors of thousands of dili- gent inquirers must have been directed to the clas- sification of animals. How could he know that the rhinoceros was of that particular species rather than _ another? and what is meant by species? ‘To trace the history of this confidence would be to tell the long story of zoological investigation; a story too long for narration here, though we may pause a while to consider its difficulties. To make a, classical catalogue of the books in the British Museum would be a gigantic task; but imagine what that task would be if all the title- pages and other external indications were destroy-. ed! The first attempts would necessarily be of a rough approximative kind, merely endeavoring to make a sort of provisional order amid the chaos, after which succeeding labors might introduce bet- ter and better arrangements. ‘T'he books might first be grouped according to size; but, having got them together, it would soon be discovered that size was no indication of their contents: quarto poems and duodecimo histories, octavo grammars and folio dictionaries, would immediately give warning that some other arrangement was needed, Nor would it be better to separate the books according to the languages in which they were written. ‘The pres- 88 STUDIES IN ANIMAL LIFE. ence or absence of “illustrations” would furnish no better guide, while the bindings would soon be found to follow no rule. Indeed, one by one, all the external characters would prove unsatisfactory, and the laborers would finally have to decide upon some internal characters. Having read enough of each book to ascertain whether it was poetry or prose—and, if poetry, whether dramatic, epic, lyric, or satiric; and if prose, whether history, philoso- phy, theology, philology, science, fiction, or essay— a rough classification could be made; but even then there would be many difficulties, such as where to place a work on the philosophy of history—or the history of science—or theology under the guise of sclence—or essays on very different subjects, while some works would defy classification. Gigantic as this labor would be, it would be tri- fling compared with the labor of classifying all the animals now living (not to mention extinct species), so that the place of any one might be securely and rapidly determined; yet the persistent zeal and sa- gacity of zoologists have done for the animal king- dom what has not yet been done for the library of the Museum, although the titles of the books are not absent. It has been done by patient reading of the contents—by anatomical investigation of the in- ternal structure of animals. Except on a basis of comparative anatomy, there could have been no better a classification of animals than a classification of books according to size, language, binding, ete. STUDIES IN ANIMAL LIFE. 89 An unscientific Pliny might group animals accord- ing to their habitat; but when it was known that whales, though living in the water and swimming hike fishes, were in reality constructed like air- breathing quadrupeds—when it was known that animals differmg so widely as bees, birds, bats, and flying squirrels, or as otters, seals, and cuttlefish, lived together in the same element, it became ob- © _ vious that such a principle of arrangement could lead to no practical result. Nor would it suffice to class animals according to their modes of feeding, since in all classes there are samples of each mode. Kqually unsatisfactory would be external form— the seal and the whale resembling fishes, the worm resembling the eel, and the eel the serpent. T'wo things were necessary: first, that the struc- ture of various animals should be minutely studied and described—which is equivalent to reading the books to be classified; and, secondly, that some ar- tificial method should be devised of so arranging the immense mass of details as to enable them to be re- membered, and also to enable fresh discoveries readi- ly to find a place in the system. We may be per- fectly familiar with the contents of a book, yet wholly at a loss where to place it. If we have to catalogue Hegel’s Philosophy of History, for exam- ple, it becomes a difficult question whether to place it under the rubric of philosophy, or under that of history. ‘To decide this point, we must have some system of classification. 90 STUDIES IN ANIMAL LIFE. In the attempts to construct a system, naturalists are commonly said to have followed two methods, the artificial and the natural. The artificial method seizes some one prominent characteristic, and groups all the individuals together which agree in this one respect. In Botany the artificial method classes plants according to the organs of reproduction; but this has been found so very imperfect that it has been abandoned, and the natural method has been substituted, according to which the whole structure of the plant determines its place. If flying were taken as the artificial basis for the grouping of some animals, we should find insects and birds, bats and flying squirrels grouped together; but the natural method, taking into consideration not one character, but all the essential characters, finds that insects, birds, and bats differ profoundly in their organiza- tion: the insect has wings, but its wings are not - formed like those of the bird, nor are those of the bird formed like those of the bat. The insect does not breathe by lungs, like the bird and the bat; it has no internal skeleton, like the bird and the bat; and the bird, although it has many points in com- mon with the bat, does not, like it, suckle its young; and thus we may run over the characters of each organization, and find that the three animals belong to widely different groups. It is to Linnzeus that we are indebted for the most ingenious and comprehensive of the many schemes invented for the cataloguing of animal STUDIES IN ANIMAL LIFE. 91 forms, and modern attempts at classification are only improvements on the plan he laid down. First we may notice his admirable invention of the double names. It had been the custom to designate plants and animals according to some name common to a large group, to which was added a description more or less characteristic. An idea may be formed of the necessity of a reform by conceiving what a la- borious and uncertain task it would be if our friends spoke to us of having seen a dog in the garden, and on our asking what kind of a dog, instead of their saying ‘a terrier, a bull-terrier, or a Skye-terrier,” they were to attempt a description of the dog. Something of this kind was the labor of under- standing the nature of an animal from the vague description of it given by naturalists. Linnzeus rebaptized the whole animal kingdom upon one intelligible principle. He continued to employ the name common to each group, such as that of Felis for the cats, which became the generic name; and in lieu of the description which was given of each different kind to indicate that it was a lion, a tiger, a leopard, or a domestic cat, he affixed a specific name: thus the animal bearing the description of a lion became Felis leo; the tiger, Felis tigris ; the leopard, Felis leopardus ; and our domestic friend, Felis catus. These double names, as Vogt remarks, are like the Christian- and sur-names by which we distinguish the various members of one family ; and instead of speaking of Tomkinson with the flabby 92, STUDIES IN ANIMAL LIFE. face and Tomkinson with the square forehead, we simply say John and William T'’omkinson. Linnzeus did more than this. He not only fixed definite conceptions of species and genera, but in- troduced those of orders and classes. Cuvier added families to genera, and sub-kingdoms (embranche- ments) to classes. Thus a scheme was elaborated by which the whole animal kingdom was arranged in subordinate groups: the sub-kingdoms were di- vided into classes, the classes into orders, the orders into families, the families into genera, the genera into species, and the species into varieties. The euiding principle of anatomical resemblance determ- ined each of these divisions. Those largest groups, which resemble each other only in having what is called the typical character in common, are brought together under the first head. Thus all the groups which agree in possessing a backbone and internal skeleton, although they differ widely in form, struc- ture, and habitat, do nevertheless resemble each other more than they resemble the groups which have no backbone. This great division having been formed, it is seen to arrange itself in very obvious minor divisions or classes—the mammalia, birds, reptiles, and fishes. All mammals resemble each other more than they resemble birds; all reptiles resemble each other more than they resemble fishes (in spite of the superficial resemblance between ser- pents and eels or lampreys). Tach class, again, falls into the minor groups of orders, and on the STUDIES IN ANIMAL LIFE. 93 same principles—the monkeys being obviously dis- tinguished from rodents, and the carnivora from the ruminating animals; and so of the rest. In each order there are generally families, and the families fall into genera, which differ from each other only in fewer and less important characters. The genera include groups which have still fewer differences, and are called species; and these, again, include groups which have only minute and unimportant differences of color, size, and the like, and are call- ed sub-species, or varieties. Whoever looks at the immensity of the animal kingdom, and observes how intelligibly and system- atically it is arranged in these various divisions, will admit that, however imperfect, the scheme is a magnificent product of human ingenuity and labor. It is not an arbitrary arrangement, like the group- ing of the stars in constellations; it expresses, though obscurely, the real order of Nature. All true classification should be to forms what laws are to phenomena; the one reducing varieties to sys- tematic order, as the other reduces phenomena to their relation of sequence. Now if it be true that the classification expresses the real order of Nature, and not simply the order which we may find con- venient, there will be something more than mere resemblance indicated in the various groups; OT, rather let me say, this resemblance itself is the con- sequence of some community in the things com- pared, and will therefore be the mark of some deep- 94 STUDIES IN ANIMAL LIFE. er cause. What is this cause? Mr. Darwin holds that “propinquity of descent—the only known cause of the similarity of organic beings—is the bond, hidden as it is by various degrees of modifi- cation, which is partially revealed to us by our classifications” *—“ that the characters which natu- ralists consider as showing true affinity between any two or more species are those which have been inherited from a common parent, and in so far all true classification is genealogical; that community of descent, is the hidden bond which naturalists have been unconsciously seeking, and not some unknown plan of creation, or the enunciation of general propositions, and the mere putting together and separating objects more or less alike.” + Before proceeding to open the philosophical dis- cussion which inevitably arises on the mention of Mr. Darwin’s book, I will here set down the chief groups, according to Cuvier’s classification, for the benefit of the tyro in natural history, who will easi- ly remember them, and will find the knowledge constantly invoked. There are four sub-kingdoms, or branches: 1. Vertebrata; 2. Mollusca; 8. Articulata; 4. Radi- ata. The VERTEBRATA consist of four classes: Mam- malia, Birds, Reptiles, and Fishes. The Mouuusca consist of six classes: Cephalo- poda (cuttlefish), Pteropoda, Gasteropoda (snails, * Darwin: Origin of Species, p. 414. + Ibid., p. 420. STUDIES IN ANIMAL LIFE. 95 etc.), Acephala (oysters, etc.), Brachiopoda, and Cir- rhopoda (barnacles).—N.B. This last class is now removed from the Mollusks and placed among the Crustaceans. The ARTICULATA are composed of four classes: Annelids (worms), Crustacea (lobsters, crabs, etc.), Arachnida (spiders), and Insecta. The RADIATA embrace all the remaining forms; but this group has been so altered since Cuvier’s time that I will not burden your memory just now with an enumeration of the details. The reader is now in a condition to appreciate the general line of argument adopted in the discus- sion of Mr. Darwin’s book, which is at present ex- citing very great attention, and which will, at any rate, aid in general culture by opening to many minds new tracts of thought. The benefit in this direction is, however, considerably lessened by the extreme vagueness which is commonly attached to the word ‘‘species,” as well as by the great want of philosophic culture which impoverishes the major- ity of our naturalists. JI have heard or read few arguments on this subject which have not impress- ed me with the sense that the disputants really at- tached no distinct ideas to many of the phrases they were uttering. Yet it is obvious that we must first settle what are the facts grouped together and indi- cated by the word “species,” before we can carry on any discussion as to the origin of species. ‘To be battling about the fixity or variability of species, 96 STUDIES IN ANIMAL LIFE. without having rigorously settled what species is, can lead to no edifying result. It is notorious that if you ask even a zoologist, | What is a species? you will always find that he has only a very vague answer to give; and if his answer be precise, it will be the precision of error, and will vanish into contradictions directly it is ex- amined. ‘The consequence of this is, that even the ablest zoologists are constantly at variance as to specific characters, and often can not agree whether an animal shall be considered of a new species or only a variety. There could be no such disagree- ments if specific characters were definite—if we knew what species meant, once and for all. Aska chemist, What is a salt? What an acid? and his reply will be definite and uniformly the same: what he says all chemists will repeat. Not so the zoologist. Sometimes he will class two animals as of different species, when they only differ in color, in size, or in the numbers of tentacles, ete.; at other times he will class animals as belonging to the same species, although they differ in size, color, shape, in- stincts, habits, etc. The dog, for example, is said to be one species with many varieties or races. But contrast the pug-dog with the greyhound, the span- iel with the mastiff, the bull-dog with the Newfound- land, the setter with the terrier, the sheep-dog with the pointer; note the striking differences in their structure and their instincts, and you will find that they differ as widely as some genera and as some STUDIES IN ANIMAL LIFE. 97 species. If these varieties inhabited different coun- tries—if the pug were peculiar to Australia and the mastiff to Spain—there is not a naturalist but would class them as of different species. The same re- mark applies to pigeons and ducks, oxen and sheep. The reason of this uncertainty is that the thing species does not exist: the term expresses an ab- straction, like virtue, or whiteness; not a definite concrete reality, which can be separated from other things, and always be found the same. Nature pro- duces individuals; these individuals resemble each other in varying degrees; according to their resem- blances we group them together as classes, orders, genera, and species; but these terms only express the relations of resemblance, they do not indicate the existence of such things as classes, orders, genera, or species.* ‘There is a reality indicated by each term —that is to say, a real relation; but there is no ob- jective existence of which we could say, This is variable, This is immutable. Precisely as there is a real relation indicated by the term goodness, but there is no goodness apart from the virtuous actions and feelings which we group together under this term. It is true that metaphysicians in past ages angrily debated respecting the immutability of vir- tue, and had no more suspicion of their absurdity than moderns have who debate respecting the fixity * CUVIER says, in so many words, that classes, orders, and gen- era are abstractions, et rien de pareil n’existe dans la nature ; but species is zot an abstraction !—See Letires a Pfaff, p. 179. E 98 STUDIES IN ANIMAL LIFE. of species. Yet no sooner do we understand that ‘species means a relation of resemblance between animals, than the question of the fixity or varia- bility of species resolves itself into this: Can there be any variation in the resemblances of closely al- lied animals? A question which would never be asked. No one has thought of raising the question of the fixity of varieties, yet it is as legitimate as that of the fixity of species; and we might also argue for the fixity of genera, orders, classes, the fixity of all these being implied in the very terms; since no sooner does any departure from the type present. itself, than by that it is excluded from the category ; no sooner does a white object become gray or yel- low, than it is excluded from the class of white ob- jects. Here, therefore, is a sense in which the phrase “fixity of species” is indisputable; but in this sense the phrase has never been disputed. When zoolo- gists have maintained that species are variable, they have meant that animal forms are variable; and these variations, gradually accumulating, result at last in such differences as are called specific. Al- though some zoologists, and speculators who were not zoologists, have believed that the possibility of variation is so great that one species may actually be transmuted into another, 7. ¢., that an ass may be developed into a horse, yet most thinkers are now agreed that such violent changes are impossible, and that every new form becomes established only STUDIES IN ANIMAL LIFE. 99 through the long and gradual accumulation of mi- nute differences in divergent directions. It is clear, from what has just been said, that the many angry discussions respecting the fixity of spe- cies, which, since the days of Lamarck, have dis- turbed the amity of zoologists and speculative phi- losophers, would have been considerably abbrevia- ted had men distinctly appreciated the equivoque which rendered their arguments hazy. I am far from implying that the battle was purely a verbal one. I believe there was a real and important dis- tinction in the doctrines of the two camps; but it seems to me that, had a clear understanding of the fact that species was an abstract term been uniform- ly present to their minds, they would have sooner come to an agreement. Instead of the confusing disputes as to whether one species could ever be- come another species, the question would have been, Are animal forms changeable? Can the descend- ants of animals become so unlike their ancestors, in certain peculiarities of structure or instinct, as to be classed by naturalists as a different species ? No sooner is the question thus disengaged from. equivoque than its discussion becomes narrowed within well-marked limits. That animal forms are variable is disputed by no zoologist. The only question which remains is this: Zo what extent are animal forms variable? The answers given have been two: one school declaring that the extent of variability is limited to those trifling characteristics 100 STUDIES IN ANIMAL LIFE. which mark the different varieties of each species ; the other school declaring that the variability is in- definite, and that all animal forms may have arisen from successive modifications of a very few types, or even of one type. Now I would call your attention to one point in this discussion which ought to be remembered when antagonists are growing angry and bitter over the subject; it is, that both these opinions are necessa- rily hypothetical—there can be nothing like posi- tive proof adduced on either side. The utmost that either hypothesis can claim is that it is more con- sistent with general analogies, and better serves to bring our knowledge of various points into har- mony. Neither of them can claim to be a truth which warrants dogmatic decision. Of these two hypotheses, the first has the weight and majority of authoritative adherents. It de- clares that all the different kinds of bats, for exam- ple, were distinct and independent creations, each species being originally what we see it to be now, and what it will continue to be as long as it ex- ists: lions, panthers, pumas, leopards, tigers, jagu- ars, ocelots, and domestic cats being so many origr- nal stocks, and not so many divergent forms of one orig- mal stock. ‘The second hypothesis declares that all these kinds of cats represent divergencies of the original stock, precisely as the varieties of each kind represent the divergencies of each species. It is true that each species, when once formed, only ad- STUDIES IN ANIMAL LIFE. 101 mits of limited variations; any cause which should push the variation beyond certain limits would de- stroy the species, because by species is meant the group of animals contained within those limits. Let us suppose the original stock from which all these kinds of cats have sprung to have become modified into lions, leopards, and tigers—in other words, that the gradual accumulation of divergencies has re- sulted in the whole family of cats existing under these three forms. The lions will form a distinct species; this species varies, and in the course of long variation a new species, the puma, rises by the side of it. The leopards also vary, and let us sup- pose their variation at length assumes so marked a form—in the ocelot—that we class it as a new spe- cies. ‘There is nothing in this hypothesis but what is strictly consonant with analogies; it is only ex- tending to species what we know to be the fact with respect to varieties; and these varieties which we know to have been produced from one and the same species are often more widely separated from each other than the lion is from the puma, or the leopard from the ocelot. Mr. Darwin remarks that ‘at least a score of pigeons might be chosen, which, if shown to an ornithologist, and he were told that they were wild birds, would certainly, I think, be ranked by him as well-defined species. Moreover, I do not believe that any ornithologist would place the English carrier, the short-faced tumbler, the runt, the barb, the pouter, and fantail in the same 102 STUDIES IN ANIMAL LIFE. genus, more especially as in each of these breeds several truly-inherited sub-breeds or species, as he might have called them, could be shown him.” The development of numerous specific forms, widely distinguished from each other, out of one common stock, is not a whit more improbable than the development of numerous distinct languages out of a common parent language, which modern philologists have proved to be indubitably the case. Indeed, there is a very remarkable analogy between philology and zoology in this respect: just as the comparative anatomist traces the existence of simi- lar organs, and similar connections of these organs, throughout the various animals classed under one type, so does the comparative philologist detect the family likeness in the various languages scattered from China to the Basque Provinces, and from Cape Comorin across the Caucasus to Lapland—a like- ness which assures him that the Teutonic, Celtic, Wendic, Italic, Hellenic, Iranic, and Indic languages are of common origin, and separated from the Ara- bian, Aramean, and Hebrew languages, which have another origin. let us bring together a French- man, a Spaniard, an Italian, a Portuguese, a Walla- chian, and a Rheetian, and we shall hear six very different languages spoken, the speakers severally unintelligible to each other, their languages differ- ing so widely that one can not be regarded as the modification of the other; yet we know most posi- tively that all these languages are offshoots from STUDIES IN ANIMAL LIFE. 108 the Latin, which was once a living language, but which is now, so to speak, a fossil. The various species of cats do not differ more than these six languages differ, and yet the resemblances point in each case to a common origin. Max Muller, in his brilliant essay on Comparative Mythology,* has said, “Tf we knew nothing of the existence of Latin— if all historical documents previous to the fifteenth century had been lost—if tradition, even, was silent as to the former existence of a Roman empire, a mere comparison of the six Roman dialects would enable us to say that at some time there must have been a language from which all these modern dia- lects derived their origin in common; for without this supposition it would be impossible to account for the facts exhibited by these dialects. Let us look at the auxilary verb. We find: Italian. Wallachian. Rhetian. Spanish. Portuguese. French. ILO SBE oedodeo sono sumsunt sunt soy sou. suis. PE DOUN ATG: <5 cis's: 30's sei es eis eres es es. TTC WIS 7. Sieie.s aieie'ess e é (este) ei es he est. WVGLATO) S's creie,s ie siamo suntemu essen somos somos sommes. VOUVATO!\< cisiseisies siete sunteti esses sois sois étes (estes). ANoG\y Che So aogde sono sunt ean (sun) son 520 sont. It is clear, even from a short consideration of these forms, first, that all are but varieties of one common type; secondly, that it is impossible to consider any one of these six paradigms as the original from which the others had been borrowed. ‘To this we may add, thirdly, that m none of the languages to which these verbal forms belong do we find the * See Oxford Essays, 1856. 104 STUDIES IN ANIMAL LIFE. elements of which they could have been composed. If we find such forms as 7’av avmé, we can explain them by a mere reference to the radical means which French has still at its command, and the same may be said even of compounds like j’avmera, 1. e., je- aimer-at, I have to love, [shalllove. But a change from je suis to tu es is inexplicable by the light of French grammar. These forms could not have grown, so to speak, on French soil, but must have been handed down as relics from a former period— must have existed in some language antecedent to any of the Roman dialects. Now, fortunately, in this case, we are not left to a mere inference, but as we possess the Latin verb, we can prove how, by phonetic corruption and by mistaken analogies, every one of the six paradigms is but a national metamorphosis of the Latin original. ‘Let us now look at another set of paradigms: +, Lithu- a Old “ : Sanscrit. aap Zend. Doric. Sigvonies Latin. Gothic. Armen. Ienmlos ASaaboor 4smi esmi ahmi éupuc yesme sum im em. OWI sec. warp Butwer Lytton, Bart. Li- brary Edition. 12mo, Muslin. SQUIER’S NICARAGUA. Nicaragua: Its People, Scenery, Monuments, Resources, Condi- tions, and proposed Canal. With One Hundred Maps and Illustra- tions. By E. G. Squier, formerly Chargé d’Affaires of the United States to the Republics of Central. America. A Revised Edition. 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