Part 2 (1/2)

It was with a view of the animal kingdom not much clearer than this that Huxley began his work on the Medusae of the tropic seas. He began to study them no doubt simply because they were among the most abundant of the animals that could be obtained from the s.h.i.+p. He made endless dissections and drawings, and, above all, studied their minute anatomy with the microscope. They were all placed among Cuvier's _Radiata_, but, as Huxley said in the first line of his memoir:

”Perhaps no cla.s.s of animals has been investigated with so little satisfactory and comprehensive result, and this not for the want of patience and ability on the part of the observers, but rather because they have contented themselves with stating matters of detail concerning particular genera and species, instead of giving broad and general views of the whole cla.s.s, considered as organised upon a given type, and inquiring into its relations with other families.”

He found that fully developed Medusae consisted each of a disc with tentacles and vesicular bodies at the margins, a stomach, and ca.n.a.ls proceeding from it, and generative organs. He traced this simple common structure through the complications and modifications in which it appeared in the different groups of Medusae, in all this work bringing out the prevailing features of the anatomy in contrast to the individual peculiarities. He shewed that microscopically all the complicated systems of ca.n.a.ls and organs were composed of two ”foundation-membranes,” two thin webs of cells, one of which formed the outermost layer of the body, while the inner formed the lining of the stomach and ca.n.a.ls in the thinner parts of the body, such as the edges of the umbrella-like disc, and towards the ends of the tentacles. These thin webs formed practically all the body. In the thicker parts there was interposed between them an almost structureless layer of jelly, placed like padding between the lining and the cloth of a coat. He shewed that blood-vessels and blood were absent, in which he has been confirmed by all other observers. He declared more doubtfully against the existence of a special nervous system, and it was not until long after, when the methods of microscopic investigation were much more perfect, that the delicate nerve-cells and nerve-fibres, which we now know to exist, were discovered.

Having thus shewn the peculiar organisation of the group he turned to seek out its allies among other families. The Medusae consisted essentially of two membranes inclosing a variously shaped cavity inasmuch as all its organs were so composed. The generative organs were external, being variously developed processes of the two membranes. The peculiar organs called thread-cells--poisoned darts by the discharge of which prey could be paralysed--were universally present. What other families presented these peculiarities?

There are to be found abundantly in sea-water, and less frequently in fresh water, innumerable forms of animal life called Zoophytes or animal plants because they occur as encrusting ma.s.ses like lichens, or branched forests like moss, on the surface of stones and sh.e.l.ls. A common habit gave this set of creatures their common name; but, although they were grouped together, there was no greater affinity among them than there is racial affinity among people who clothe themselves for an evening party in the same conventional dress. Huxley examined a large number of these, and picked out from them two great families of polyps, the Hydroid and Sertularian polyps, which each consist of colonies of creatures very much like the little fresh-water hydra. He shewed that the tubular body of these and the ring of tentacles surrounding the mouth were composed of the same two foundation-membranes of which all the organs of Medusae are composed.

He found in them the poisoned arrows or thread-cells of the Medusae, and the same external position of the reproductive organs. And, lastly, he separated from all other creatures, and a.s.sociated with his new group, some of the strangest and most beautiful animals of the tropic seas, known to science as the Physophoridae and the Diphyidae.

The best-known of these is the ”Portuguese man-of-war,” the body of which consists of a large pear-shaped vesicle which floats on the water like a bladder. From the lower part of this depend into the water large and small nutritive branches, each ending in a mouth surrounded by a circle of waving tentacles armed with batteries of thread-cells, while another set of hanging protrusions bear the grape-like reproductive organs. On the upper surface of the bladder is fixed a purple sail of the most brilliant colour, by which the floating creature is blown through the water. When the weather is rough, the bladder empties, and the creature sinks down into the quiet water below the waves, to rise again when the storm is over. This, and its equally wonderful allies, Huxley showed to be a complicated colony of hydra-like creatures, each part being composed of two membranes, and therefore essentially similar to Medusae. Thus, by a great piece of constructive work, an a.s.semblage of animals was gathered into a new group and shewn to be organised upon one simple and uniform plan, and, even in the most complex and aberrant forms, reducible to the same type. The group, and Huxley's conception of its structure, are now absolutely accepted by anatomists, and have made one of the corner-stones of our modern idea of the arrangement of the animal kingdom. With the exception of sponges, concerning the exact relations of which there is still dispute, and of a few sets of parasitic and possibly degenerate creatures, all animals, the bodies of which are multicellular, from the simple fresh-water hydra up to man, are divided into two great groups. The structure of the simpler of these groups is exactly what Huxley found to be of importance in the Medusae. The body wall, from which all the organs protrude, consists merely of a web of cells arranged in two sheets or membranes, and the single cavity consists of a central stomach, surrounded by these membranes, the cavity remaining simple or giving rise to a number of branching ca.n.a.ls. The members of this great division of the animal kingdom are the creatures which Huxley selected and placed together, with the addition of the sea-anemones and the medusa-like Ctenophora, which, indeed, he mentioned in his memoir as being related to the others, but reserved fuller consideration for a future occasion. This group is now called the Clenterata, the name implying that the creatures are simply hollow stomachs, and it is contrasted in the strongest way with the group Clomata, in which are placed all the higher animals, from the simplest worm up to man; animals in which, in addition to the two foundation-membranes of the Clenterata, there is a third foundation-membrane, and in which, in addition to the simple stomach cavity with its offshoots, there is a true body-cavity or clome, and usually a set of s.p.a.ces and channels containing a blood-fluid. The older method of naming groups of animals after some obvious superficial character lingered on for some years in text-books and treatises, but in this memoir the young s.h.i.+p-surgeon had replaced it by the modern scientific method of grouping animals together only because of real ident.i.ty of structure.

There is yet left to be noticed perhaps the most wonderful of all the ideas in this first memoir by Huxley. In the course of describing the two foundation membranes of the Medusae he remarks:

”It is curious to remark, that throughout, the outer and inner membranes appear to bear the same physiological relation to one another as do the serous and mucous layers of the germ: the outer becoming developed into the muscular system, and giving rise to the organs of offence and defence: the inner on the other hand appearing to be more closely subservient to the purposes of nutrition and generation.”

In the whole range of science it would be difficult to select an utterance more prophetic of future knowledge than these few words.

Huxley had been reading the investigations of Von Baer into the early development of back-boned animals. He had learned from them the great generalisation, that the younger stages of these animals resemble one another more closely than the adult stages, and that in an early stage in the development of all these animals the beginning of the embryo consists of two layers of cells, in fact of two foundation-membranes, one forming specially the wall of the future digestive ca.n.a.l, the other forming the most external portion of the future animal. In these days nothing could have seemed a remoter or more unlikely comparison than one inst.i.tuted between Medusae and the embryonic stages of back-boned animals. But Huxley made it, not allowing the evidence brought before his reason to be swamped by preconceived ideas. At the time he did no more than to make the comparison. It was much later that the full importance of it became known, when more extended work on the embryology of vertebrates and of the different groups of the invertebrates had made it plain that the two foundation-membranes of Huxley occur in all animals from the Medusae up to man. In the group of Clenterata the organisation remains throughout life as nothing more than a folding in and folding out of these membranes. The early stages of all the higher animals similarly consist of complications of the two membranes; but later on there is added to them a third membrane. Thus the group that Huxley gathered together comprises those animals that as adults remain in a condition of development which is pa.s.sed through in the embryonic life of all higher animals. The immense importance of this conclusion becomes plain, and the conclusion itself seems obvious, when seen in the light of the doctrine of descent. The group of Clenterata represents a surviving, older condition in the evolution of animals. Huxley himself, when on the _Rattlesnake_, regarded evolution only as a vague metaphysical dream, and he made the comparison which has been described without any afterthought of what it implied. In this we have the earliest authentic instance of the peculiar integrity of mind which was so characteristic of him in his dealings with philosophy and tradition. He never allowed any weight of authority or any apparent disturbance of existing ideas to alter the conclusions to which his reason led him. This intellectual courage made him fitted to be the leader in the battle for evolution and against traditional thought, and we shall find again and again in consideration of his work that it was the keynote of his life.

CHAPTER IV

EARLY DAYS IN LONDON

Scientific Work as Unattached s.h.i.+p-Surgeon--Introduction to London Scientific Society--Translating, Reviewing, and Lecturing--Ascidians--Molluscs and the Archetype--Criticism of Pre-Darwinian Evolution--Appointment to Geological Survey.

The _Rattlesnake_ was paid off at Chatham on November 9, 1850. In the natural course of events Huxley would have been appointed before long to active service upon another s.h.i.+p. But he had no intention of relapsing into the position of a mere navy doctor; he had acc.u.mulated sufficient scientific material to keep him employed on scientific investigation for years, and so he applied to the Admiralty to ”be borne on the books” of H.M.S. _Fisgard_ at Woolwich,--that is to say, to be appointed a.s.sistant-surgeon to the s.h.i.+p ”for particular service,” so that he should not be compelled to live on board, but might remain in town, and, with free access to libraries and museums, work up the observations he had made on the _Rattlesnake_ into serious and substantial contributions to science. His request was granted, largely by the aid of his old chief, Sir W. Burnett, who continued to take the most useful interest in the young man he had originally nominated to the service. In a letter to him Huxley described the investigations which he desired to continue as being chiefly those on ”the anatomy of certain Gasteropod and Pteropod Mollusca, of Firola and Atlantis, of Salpa and Pyrosoma, of two new Ascidians, namely, Appendicularia and Doliolum, of Sagitta and certain Annelids, of the auditory and circulatory organs of certain transparent Crustacea, and of the Medusae and Polyps.” His request was granted, and for the next three years Huxley lived in London with his brother, on the exiguous income of an a.s.sistant-surgeon, and devoted himself to research. He became almost at once of the first rank among English anatomists. The result of the paper on Medusae in the _Transactions of the Royal Society_ was that he was elected a Fellow of the Society on June 5, 1851, and a year later received a Royal Medal of the Society. He made many warm friends.h.i.+ps both among the older and the younger generations of scientific men. In his obituary notice of Huxley, Sir Michael Foster wrote:

”By Edward Forbes, in whose nature there was much that was akin to his own, and with whom he had some acquaintance before his voyage, he was at once greeted as a comrade, and with Joseph Dalton Hooker, to whom he was drawn at the very first by their common experience as navy surgeons, he began an attachment which, strengthened by like biological aspirations, grew closer as their lives went on. In the first year after his return, in the autumn of 1851, he made the acquaintance of John Tyndall at the meeting of the British a.s.sociation at Ipswich, and the three, Hooker, Huxley, and Tyndall, finding how much in common were all their scientific views and desires, formed then and there a triple scientific alliance.”

Repeated efforts were made by these three, and by more influential friends, to induce the Admiralty to contribute to the expense of publis.h.i.+ng Huxley's scientific results, as they had given a pledge to encourage officers who had done scientific work. These efforts lasted unavailingly for nearly three years, and then, as Huxley says: ”The Admiralty, getting tired, I suppose, cut short the discussion by ordering me to join a s.h.i.+p, which thing I declined to do, and, as Rastignac, in the _Pere Goriot_, says to Paris, I said to London, _ nous deux_.” This light phrase conceals a courageous and momentous decision. He was absolutely without private resources, and having abandoned his professional work he had no salary of any kind. For a year or so he supported himself by writing reviews and popular scientific articles, striving all the time not only to gain his bread but to continue his scientific work and make it known to the public.

He desired to get a professors.h.i.+p of physiology or of comparative anatomy, and as vacancies occurred he applied, but unsuccessfully. At the same time, he tells us, he and his friend, John Tyndall, were

”candidates, he for the Chair of Physics, and I for that of Natural History in the University of Toronto, which, fortunately, as it turned out, would not look at either of us. I say fortunately, not from any lack of respect for the University of Toronto; but because I soon made up my mind that London was the place for me, and hence I have steadily declined the inducements to leave it which have at various times been offered.”

In these early years in London Huxley's work was most varied. A large number of anonymous articles by him appeared in the _Literary Gazette_, and in other periodicals. He a.s.sisted to remove the insular narrowness from English scientific work by translating many foreign memoirs. With the collaboration of Mr. Henfrey, he edited a series of scientific memoirs, all of which were translated from foreign languages, and many by his own pen. With the a.s.sistance of Mr. George Busk he made a translation of Kolliker's _Histology_, a great treatise on microscopic anatomy which played a large part in the development of the modern English schools of anatomy and physiology. He made some valuable contributions to Todd and Bowman's _Cyclopaedia of Anatomy_, an elaborate publication now nearly forgotten and practically superseded, but which was the standard anatomical work of the middle of this century. He was unable to progress rapidly with his work upon oceanic Medusae, as he was uncertain how to have it published; the Admiralty refused to a.s.sist, and it was too lengthy for publication in the volumes of the learned Societies. As a matter of fact, he did not publish it until 1858, when it appeared as a separate memoir. To the _Quarterly Journal of Microscopical Science_ and to the _Transactions of the Royal and Linnaean Societies_ he contributed a large number of memoirs dealing with the microscopic anatomy and relations.h.i.+ps of invertebrates, and, lastly, he gave a series of addresses at the Royal Inst.i.tution, which had been founded as a means by which leading men of science might give accounts of their work to London society. Abstracts of these lectures are published in the early volumes of the _Proceedings of the Royal Inst.i.tution_ and are interesting as shewing the kinds of zoological subjects which were attracting the attention of Huxley and which he considered of sufficient interest and importance to bring to the notice of the general public. The first of these lectures, and probably the first given in public by Huxley, occurred on April 30, 1852, and was ent.i.tled ”Animal Individuality.”

The problem as to what is meant by an individual had been raised in his mind by consideration of many of the forms of marine life, notably compound structures like the Portuguese man-of-war, and creatures like the salps, which form floating chains often many yards in length. He explained that the word _individual_ covers at least three quite different kinds of conceptions. There is, first, what he described as arbitrary individuality, an individuality which is given by the mind of the observer and does not actually exist in the thing considered. Thus a landscape is in a sense an individual thing, but only so far as it is a particular part of the surface of the earth, isolated for the time in the mind of the person looking at it. If the observer s.h.i.+ft his position, the range of the landscape alters and becomes something else. Next there are material, or practically accidental individual things, such as crystals or pieces of stone; and, lastly, there are living individuals which, as he pointed out, were cycles. All living things are born into the world, grow up, and die, and it was to the cycle of life, from the egg to the adult which produces eggs, that he gave the name individual. In a simple animal like Hydra there is no difficulty in accepting this plain definition of individuality; but Huxley went on to compare with Hydra a compound creature like the Portuguese man-of-war, which really is composed of a colony of Hydra-like creatures, the different members of the colony being more or less altered to serve different functions. All these have come from the branching of a single simple creature produced from an egg, and to the whole colony Huxley gave the name of zoological individual. The salps give a still wider interpretation to this view of individuality. The original salp produced from the egg gives rise to many salps, which may either remain attached in a chain, or, breaking away from one another, may live separately. Huxley extended the use of the word _individual_ so as to include as a single zoological individual the whole set of creatures cohering in chains or breaking apart, which had been produced by budding from the product of a single egg-cell. This subtle a.n.a.lysis of ideas delighted and interested his contemporaries, and the train of logical examination of what is meant by individuality has persisted to the present time. Like all other zoological ideas, this has been considerably altered by the conception of evolution. Zoologists no longer attempt to stretch logical conceptions until they fit enormous and different parts of the living world. They recognise that the living world, because it is alive, is constantly changing, and that living things pa.s.s through different stages or kinds of individuality in the course of their lives. A single egg-cell is one kind, perhaps the simplest kind, of zoological individual; when it has grown up into a simple polyp it has pa.s.sed into a second grade of individuality; when, by budding, the polyp has become branched, a third grade is reached, and when the branches have become different, in obedience to the different purposes which they are to serve in the whole compound creature, a still further grade is reached. Huxley's attempt to find a meaning for individuality that would apply equally to a single simple creature, to a compound creature, and to the large number of separate creatures, all developed by budding from one creature, is a striking instance of his singular capacity for bringing apparently dissimilar facts into harmony, by finding out the common underlying principle, and, although we no longer accept this particular conclusion, we cannot fail to notice in it the peculiar powers of his mind.

A second and even more interesting Royal Inst.i.tution lecture dealt with the ”Ident.i.ty of Structure in Animals and Plants.” At the present time every educated person knows that the life of animals and plants alike depends on the fact that their bodies are composed of a living material called protoplasm, a material which is identical in every important respect in both kingdoms of the living world. In the early fifties, scientific opinion was by no means clear on this matter, and certainly public opinion was most vague. Huxley discussed what was meant by organisation, and shewed that in every essential respect plants and animals alike were organised beings. Then he went on to explain the cellular theory of Schwann, which was then a novelty to a general audience. Schwann, in studying the microscopic structure of plants, noticed that their bodies were made up of little cases with firm walls; these he called _cells_, and declared that the whole body of the plant was composed of cells. As the walls of these cells were the most obvious and visible feature, it was supposed that they were the most essential part of the structure, and there was some difficulty in applying the cellular theory to the bodies of animals, as in most cases there are no easily visible cell-walls in animal tissues. As the result of his own observation, and from his reading of the work of others, Huxley laid down in the clearest way what is now accepted by everyone--that the presence of walls is of minor importance, and that it is the slimy contents of the cells, what is called ”protoplasm,” that is the important element. He declared that the protoplasm of animals was identical with the protoplasm of plants, and that plants were ”animals confined in wooden cases.” He agreed with Schwann that the cell, using the term to imply the contents rather than the wall, was of fundamental importance, and was the unit of structure of the whole world of life. On the other hand, he declared that it could not be looked at as the unit of function: he denied that the powers and properties of a living body were simply the sum of the powers and properties of the single cells. In this opinion he was not followed by physiologists until quite recently. For many years physiologists held that cells were units of function just as much as they are units of structure; but in the last ten years there has been a strong return to the opinion of Huxley.

In 1851 two very important memoirs were published in the _Transactions of the Royal Society_, which contained the results of Huxley's observations of the interesting animals known as ”tunicates.” The first of these papers begins as follows:

”The Salpae, those strange gelatinous animals, through ma.s.ses of which the voyager in the great ocean sometimes sails day after day, have been the subject of a great controversy since the time of the publication of the celebrated work of Chamisso, _De Animalibus Quibusdam e Cla.s.se Vermium Linnaeana_. In this work there were set forth, for the first time, the singular phenomena presented by the reproductive processes of these animals,--phenomena so strange, and so utterly unlike anything then known to occur in the whole province of zoology, that Chamisso's admirably clear and truthful account was received with almost as much distrust as if he had announced the existence of a veritable Peter Schlemihl.”

According to Chamisso, salps appeared in two forms: solitary forms, and forms in which a number of salps are united into a long chain.

Each salp of the aggregate form contains within it an embryo receiving nutrition from the mother by a connection similar to the placenta by which the embryo of a mammal receives nourishment from the blood of the mother. These embryos grow up into the solitary form, and the solitary form gives rise to a long chain of the aggregate form which developes in the interior of the body. Chamisso compared this progress to the development of insects. ”Supposing,” he said, ”caterpillars did not bodily change into b.u.t.terflies, but by a process of s.e.xual breeding produced young which grew into the ordinary adults, and that these adults, as indeed they do, gave rise to caterpillars by s.e.xual reproduction, then there would be a true alternation of generations.”

The first generation would give rise to a second generation totally unlike itself, and this second generation would reproduce, not its kind, but the first generation; such an alternation of generations he stated to occur among the salps. Huxley had an excellent opportunity to study this question at Cape York in November, 1849. ”For a time the sea was absolutely crowded with Salpae, in all stages of growth, and of size very convenient for examination.” He was able to verify the general truth of Chamisso's statement. The aggregate form of Salpa always gives rise to the solitary salps, and the solitary salps always give rise to chains of the aggregate salps. But the process of reproduction he shewed to be quite different in the two cases. The solitary salp produces in its interior a little stolon or diverticulum which contains an outgrowth from the circulatory system, and this stolon gradually becomes pinched off into the members of the chain of the aggregate form. The salps of the aggregate form are therefore merely buds from the solitary form, and are not produced in the ordinary way, by s.e.xual generation. On the other hand, each salp of the chain has within it a true egg-cell. This is fertilised by a male cell, and within the body of the parent, nourished by the blood of the parent, grows up into the solitary form. There is then an alternation of generations, but there are not two s.e.xual generations. The s.e.xual generation of chain salps gives rise to forms which reproduce by buds.

From this conclusion, with which all later observers have agreed, Huxley went on to his theory of individuality. Different names had been given to the two forms, but Huxley declared that neither form was a true zoological individual; they were only parts of individuals or organs, and the true individual was the complete cycle involving both forms.

In addition to determining the interesting method of reproduction, Huxley made an elaborate investigation of the structure of Salpa. On one occasion only the _Rattlesnake_ came across a quant.i.ty of an allied Ascidian, Pyrosoma, which had received its name from its phosph.o.r.escence.