"At least, with a good light and a good microscope, with the ship tolerably steady, I never failed in procuring all the information I required. The great matter is to obtain a good successive supply of specimens, as the more delicate oceanic species are usually unfit for examination within a few hours after they are taken."
"At least, with a good light and a good microscope, with the ship tolerably steady, I never failed in procuring all the information I required. The great matter is to obtain a good successive supply of specimens, as the more delicate oceanic species are usually unfit for examination within a few hours after they are taken."
Day after day, as theRattlesnakecrept from island to island, Huxley examined the animals brought up by his tow-net. He made endless dissections, and gradually accumulated a large portfolio of drawings. Much of the time he passed at Sydney was spent in libraries and museums, comparing his own observations with the recorded observations of earlier workers, and receiving from the combination of his own work and the work of others new ideas for his future investigations. It was all entirely a labour of love; it lay outside the professional duties by which he made his living, and for along time it seemed as if he was not even to gain reputation by the discoveries he knew himself to be making. He writes in his autobiography:
"During the four years of our absence, I sent home communication after communication to the 'Linnæan' Society, with the same result as that obtained by Noah when he sent the raven out of his ark. Tired at last of hearing nothing about them, I determined to do or die, and in 1849 I drew up a more elaborate paper and forwarded it to the Royal Society. This was my dove, if I had only known it; but owing to the movements of the ship I heard nothing of that either until my return to England in the latter end of the year 1850, when I found that it was printed and published, and that a huge packet of separate copies awaited me. When I hear some of my young friends complain of want of sympathy and encouragement, I am inclined to think that my naval life was not the least valuable part of my education."
"During the four years of our absence, I sent home communication after communication to the 'Linnæan' Society, with the same result as that obtained by Noah when he sent the raven out of his ark. Tired at last of hearing nothing about them, I determined to do or die, and in 1849 I drew up a more elaborate paper and forwarded it to the Royal Society. This was my dove, if I had only known it; but owing to the movements of the ship I heard nothing of that either until my return to England in the latter end of the year 1850, when I found that it was printed and published, and that a huge packet of separate copies awaited me. When I hear some of my young friends complain of want of sympathy and encouragement, I am inclined to think that my naval life was not the least valuable part of my education."
This first successful paper was a memoirOn the Anatomy and the Affinities of the Family of Medusæ, and was sent at Captain Stanley's suggestion to that officer's father, the Bishop of Norwich, who communicated it to the Royal Society. It is a curious circumstance that Huxley, who afterwards met with so virulent opposition from bishops, owed his first public success to one of them. Professor Sir Michael Foster writes of this period in Huxley's life:
"The career of many a successful man has shewn that obstacles often prove the mother of endeavour, and never was this lesson clearer than in the case of Huxley. Working amidst a host of difficulties, in want of room, in want of light, seeking to unravel the intricacies of minute structure with a microscope lashed to secure steadiness, cramped within a tiny cabin, jostled by the tumult of a crowded ship's life, with the scantiest supply of books of reference, with no one at hand of whom he could take counsel on the problems opening up before him, he gathered for himself during these four years a large mass ofaccurate, important, and in most cases novel, observations and illustrated them with skilful, pertinent drawings. Even his intellectual solitude had its good effects: it drove him to ponder over the new facts which came before him, and all his observations were made alive with scientific thought."
"The career of many a successful man has shewn that obstacles often prove the mother of endeavour, and never was this lesson clearer than in the case of Huxley. Working amidst a host of difficulties, in want of room, in want of light, seeking to unravel the intricacies of minute structure with a microscope lashed to secure steadiness, cramped within a tiny cabin, jostled by the tumult of a crowded ship's life, with the scantiest supply of books of reference, with no one at hand of whom he could take counsel on the problems opening up before him, he gathered for himself during these four years a large mass ofaccurate, important, and in most cases novel, observations and illustrated them with skilful, pertinent drawings. Even his intellectual solitude had its good effects: it drove him to ponder over the new facts which came before him, and all his observations were made alive with scientific thought."
Afterwards, in England, he received the Royal Medal of the Royal Society for this memoir on Medusæ, sharing this supreme distinction of scientific England with men so illustrious as Joule, the discoverer of the relation between force and heat, Stokes, the great investigator of optical physics, and Humboldt, the traveller, all of whom received medals in the same year. In making the presentation to Huxley, the Earl of Rosse, then President of the Royal Society, declared:
"In those papers you have for the first time fully developed their structure (that of the Medusæ), and laid the foundation of a rational theory for their classification. In your second paper, on the anatomy of Salpa and Pyrosoma, the phenomena have received the most ingenious and elaborate elucidations, and have given rise to a process of reasoning, the results of which can scarcely yet be anticipated, but must bear in a very important degree upon some of the most abstruse points of what may be called transcendental physiology."
"In those papers you have for the first time fully developed their structure (that of the Medusæ), and laid the foundation of a rational theory for their classification. In your second paper, on the anatomy of Salpa and Pyrosoma, the phenomena have received the most ingenious and elaborate elucidations, and have given rise to a process of reasoning, the results of which can scarcely yet be anticipated, but must bear in a very important degree upon some of the most abstruse points of what may be called transcendental physiology."
Many reasons make it difficult for us to realise, now, the singular novelty and importance of Huxley's memoir on the Medusæ. The first is a reason which often prevents great discoveries in almost every subject from receiving in after years their due respect. The years that have passed since 1850 have seen not only the most amazing progress in our knowledge of comparative anatomy, but almost a revolution in the methods of studying it. Huxley's work has been incorporated in the very body of science. A large number of later investigators have advanced upon the lines he laid down; and just as the superstructures of a greatbuilding conceal the foundations, so later anatomical work, although it has only amplified and extended Huxley's discoveries, has made them seem less striking to the modern reader. The present writer, for instance, learned all that he knows of anatomy in the last ten years, and until he turned to it for the purpose of this volume he had never referred to Huxley's original paper. When he did so, he found from beginning to end nothing that was new to him, nothing that was strange: all the ideas in the memoir had passed into the currency of knowledge and he had been taught them as fundamental facts. It was only when he turned to the text-books of anatomy and natural history current in Huxley's time that he was able to realise how the conclusions of the young ship-surgeon struck the Fellows and President of the Royal Society as luminous and revolutionary ideas.
In the first half of the century, a conception of the animal kingdom prevailed which was entirely different from our modern ideas. We know now that all animals are bound together by the bond of a common descent, and we seek in anatomy a clue to the degrees of relationship existing among the different animals we know. We regard the animal kingdom as a thicket of branches all springing from a common root. Some of these spring straight up from the common root unconnected with their fellows. Others branch repeatedly, and all the branches of the same stem have features in common. What we see in the living world is only the surface of the thicket, the tops of the twigs; and it is by examination of the structure of this surface that we reconstruct in imagination the whole system of branches, and know that certain twigs, from their likeness, meet each other a little way down; that others are connected only very deep down, and that others, again, spring free almost from the beginning. The fossils of beds of rock of different geological ages give us incomplete views of the surface of the thicket of life, as it was in earlier times. These views we have of the past aspects of the animal kingdom are always much more incomplete than our knowledge of the existing aspect; partly because many animals, from the softness of their bodies, have left either no fossil remains at all, or only veryimperfect casts of the external surfaces of their bodies; and partly because the turning of any animal into a fossil, and its subsequent discovery by a geologist, are occasional accidents; but, although the evidence is much less perfect than we could wish, there is enough of it to convince anatomists that existing animals are all in definite blood-relationship to each other, and to make them, in the investigation of any new animal, study its anatomy with the definite view of finding out its place in the family tree of the living world.
When Huxley made his first discoveries, entirely different ideas prevailed. The animal kingdom was supposed to offer a series of types, of moulds, into which the Creator at the beginning of the world had cast the substance of life. These types were independent of each other, and had been so since the beginning of things. Anatomists were concerned chiefly with systematic work, with detecting and recording the slight differences that existed among the numbers of animals grouped around each type. No attempt was made to see connection between type and type, for where these had been separately created there was nothing to connect them except possibly some idea in the mind of the Creator. This apparently barren attitude to nature was stronger in men's minds becauseit had inspired the colossal achievements of Cuvier, a genius who, under whatever misconceptions he had worked, would have added greatly to knowledge. As we have seen in the first chapter, Huxley, through Wharton Jones, and through his own reading, had been brought under the more modern German thought of Johannes Mueller and Von Baer. He had learned to study the problems of living nature in the spirit of a physicist making investigations into dead nature. In the anatomy of animals, as in the structure of rocks and crystals, there were to be sought out "laws of growth" and shaping and moulding influences which accounted for the form of the structures. To use the technical term, he was a morphologist: one who studied the architecture of animals not merely in a spirit of admiring wonder, but with the definite idea of finding out the guiding principles which had determined these shapes.
Not only was the prevailing method of investigation faulty, but actual knowledge of a large part of the animal kingdom was extremely limited. In the minds of most zoölogists the animal kingdom was divided into two great groups: the vertebrates and invertebrates. The vertebrate, or back-boned, animals were well known; comparatively speaking they are all built upon the type of man; and human anatomists, who indeed made up the greater number of all anatomists, using their exact knowledge of the human body, had studied many other vertebrates with minute care, and, from man to fishes, had arranged living vertebrates very much in the modern order. But the invertebrates were a vague and ill-assorted heap of animals. It was not recognised that among them there were many series of different grades of ascending complexity, and therewas no well-known form to serve as a standard of comparison for all the others in the fashion that the body of man served as a standard of comparison for all vertebrates. Here and there, a few salient types such as insects and snails had been picked out, but knowledge of them helped but little with a great many of the invertebrates. The great Linnæus had divided the animal kingdom into four groups of vertebrates: mammals, birds, reptiles, and fishes, but for the invertebrates he had done no more than to pick out the insects as one group and to call everything else "Vermes" or worms. The insects included all creatures possessed of an external skeleton or hard skin divided into jointed segments, and included forms so different as insects, spiders, crabs, and lobsters. But Vermes included all the members of the animal kingdom that were neither vertebrates nor insects. Cuvier advanced a little. He got rid of the comprehensive title Vermes—the label of the rubbish-heap of zoölogists. He divided animals into four great subkingdoms: Vertebrates, Mollusca, Articulata, Radiata. These names, however, only covered very superficial resemblances among the animals designated by them. The wordMolluscaonly meant that the creatures grouped together had soft bodies, unsupported by internal or external articulated skeletons; and this character, or, rather, absence of character, was applied alike to many totally dissimilar creatures. The termArticulataincluded not only Linnæus's insects but a number of soft-skinned, apparently jointed, worm-like animals such as the leech and earthworm. Lastly, the nameRadiatameant no more than that the organs of the creatures so designated were more or less disposed around a centre, as the sepals and petals of a flower are grouped around thecentral pistil; and it included animals so different as the starfish and sea-anemones and Medusæ. The names used in the classification were not only loosely applied but were based on the most superficial observation, and took no account of the intimate structures of the tissues and organs of the animals. With slight modifications, due to individual taste or special knowledge of small groups, later writers had followed Linnæus and Cuvier.
It was with a view of the animal kingdom not much clearer than this that Huxley began his work on the Medusæ 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 ship. He made endless dissections and drawings, and, above all, studied their minute anatomy with the microscope. They were all placed among Cuvier'sRadiata, but, as Huxley said in the first line of his memoir:
"Perhaps no class 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 class, considered as organised upon a given type, and inquiring into its relations with other families."
"Perhaps no class 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 class, considered as organised upon a given type, and inquiring into its relations with other families."
He found that fully developed Medusæ consisted each of a disc with tentacles and vesicular bodies at the margins, a stomach, and canals 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 Medusæ, in all this work bringing out the prevailing features ofthe anatomy in contrast to the individual peculiarities. He shewed that microscopically all the complicated systems of canals 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 canals 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 Medusæ 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 Zoöphytes or animal plants because they occur as encrusting masses like lichens, orbranched forests like moss, on the surface of stones and shells. 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 Medusæ are composed. He found in them the poisoned arrows or thread-cells of the Medusæ, and the same external position of the reproductive organs. And, lastly, he separated from all other creatures, and associated with his new group, some of the strangest and most beautiful animals of the tropic seas, known to science as the Physophoridæ and the Diphyidæ. 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 Medusæ. Thus, by a great piece of constructive work, an assemblage 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 Medusæ. 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 canals. 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 Cœlenterata, the name implying that the creatures are simply hollow stomachs, and it iscontrasted in the strongest way with the group Cœlomata, 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 Cœlenterata, 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 cœlome, and usually a set of spaces 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 ship-surgeon had replaced it by the modern scientific method of grouping animals together only because of real identity 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 Medusæ 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."
"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 embryoconsists of two layers of cells, in fact of two foundation-membranes, one forming specially the wall of the future digestive canal, 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 instituted between Medusæ 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 Medusæ up to man. In the group of Cœlenterata 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 passed 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 Cœlenterata represents a surviving, older condition in the evolution of animals. Huxley himself, when on theRattlesnake, 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 integrityof 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.
[Contents]
Scientific Work as Unattached Ship-Surgeon—Introduction to London Scientific Society—Translating, Reviewing, and Lecturing—Ascidians—Molluscs and the Archetype—Criticism of Pre-Darwinian Evolution—Appointment to Geological Survey.
Scientific Work as Unattached Ship-Surgeon—Introduction to London Scientific Society—Translating, Reviewing, and Lecturing—Ascidians—Molluscs and the Archetype—Criticism of Pre-Darwinian Evolution—Appointment to Geological Survey.
TheRattlesnakewas 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 ship. But he had no intention of relapsing into the position of a mere navy doctor; he had accumulated 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.Fisgardat Woolwich,—that is to say, to be appointed assistant-surgeon to the ship "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 theRattlesnakeinto 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 originallynominated 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 Medusæ 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 assistant-surgeon, and devoted himself to research. He became almost at once of the first rank among English anatomists. The result of the paper on Medusæ in theTransactions of the Royal Societywas 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 friendships 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 Association 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."
"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 Association 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 publishing Huxley's scientificresults, 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 ship, which thing I declined to do, and, as Rastignac, in thePère Goriot, says to Paris, I said to London,à 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 professorship 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."
"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 theLiterary Gazette, and in other periodicals. He assisted 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 ofwhich were translated from foreign languages, and many by his own pen. With the assistance of Mr. George Busk he made a translation of Kölliker'sHistology, 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'sCyclopædia 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 Medusæ, as he was uncertain how to have it published; the Admiralty refused to assist, 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 theQuarterly Journal of Microscopical Scienceand to theTransactions of the Royal and Linnæan Societieshe contributed a large number of memoirs dealing with the microscopic anatomy and relationships of invertebrates, and, lastly, he gave a series of addresses at the Royal Institution, 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 theProceedings of the Royal Institutionand are interesting as shewing the kinds of zoölogical 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 entitled "Animal Individuality." The problem as to what is meant by an individual had been raised inhis 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 wordindividualcovers 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 shift 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 zoölogical 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 wordindividualso as to include as a single zoölogical 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 analysis 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 zoölogical ideas, this has been considerably altered by the conception of evolution. Zoölogists 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 pass 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 zoölogical individual; when it has grown up into a simple polyp it has passed 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 Institution lecture dealt with the "Identity 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 calledcells, 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 thecontents 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 theTransactions 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 Salpæ, those strange gelatinous animals, through masses 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 Classe Vermium Linnæana. 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 zoölogy, 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."
"The Salpæ, those strange gelatinous animals, through masses 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 Classe Vermium Linnæana. 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 zoölogy, 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 theplacenta 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 butterflies, but by a process of sexual breeding produced young which grew into the ordinary adults, and that these adults, as indeed they do, gave rise to caterpillars by sexual 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 Salpæ, 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 sexual generation. On the other hand, each salp of the chain has within ita 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 sexual generations. The sexual 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 zoölogical 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 theRattlesnakecame across a quantity of an allied Ascidian, Pyrosoma, which had received its name from its phosphorescence.
"The sky was clear but moonless, and the sea calm; and a more beautiful sight can hardly be imagined than that presented from the deck of the ship as she drifted, hour after hour, through this shoal of miniature pillars of fire gleaming out of the dark sea, with an ever-waning, ever brightening, soft bluish light, as far as the eye could reach on every side. The Pyrosomata floated deep, and it was only with difficulty that some were procured for examination and placed in a bucketful of sea-water. The phosphorescence was intermittent, periods of darkness alternating with periods of brilliancy. The light commenced in one spot, apparently on the surface of one of the zoöids, and gradually spread from this as a centre in all directions; then the whole was lighted up: it remained brilliant for a few seconds, and then gradually faded and died away, until the whole mass was dark again. Friction at any point induces the light at that point, and from thence the phosphorescence spreads over the whole, while the creature isquite freshly taken; afterwards, the illumination arising from friction is only local."
"The sky was clear but moonless, and the sea calm; and a more beautiful sight can hardly be imagined than that presented from the deck of the ship as she drifted, hour after hour, through this shoal of miniature pillars of fire gleaming out of the dark sea, with an ever-waning, ever brightening, soft bluish light, as far as the eye could reach on every side. The Pyrosomata floated deep, and it was only with difficulty that some were procured for examination and placed in a bucketful of sea-water. The phosphorescence was intermittent, periods of darkness alternating with periods of brilliancy. The light commenced in one spot, apparently on the surface of one of the zoöids, and gradually spread from this as a centre in all directions; then the whole was lighted up: it remained brilliant for a few seconds, and then gradually faded and died away, until the whole mass was dark again. Friction at any point induces the light at that point, and from thence the phosphorescence spreads over the whole, while the creature isquite freshly taken; afterwards, the illumination arising from friction is only local."
Dealing with these creatures in the broad anatomical spirit with which he had studied the Medusæ, Huxley shewed the typical structure manifested in the different forms, and that was common to them and the Ascidians or sea-squirts of the seashore. In a second paper on "Appendicularia and Doliolum" he made further contributions to our knowledge of these interesting creatures. Appendicularia is a curious little Ascidian, differing from all the others in its possession of a tail. Earlier observers had obtained it on various parts of the ocean surface, but had failed entirely to detect its relationship to the ordinary Ascidians. Chamisso got it near Behring's Straits and thought that it was more nearly allied to "Venus's Girdle," a Cœlenterate. Mertens, another distinguished zoölogist, had declared that "the relation of this animal with the Pteropods (a peculiar group of molluscs) is unmistakable"; while Müller, a prince among German anatomists, confessed that "he did not know in what division of the animal kingdom to place this creature." Huxley shewed that it possessed all the characteristic features of the Ascidians, the same arrangement of organs, the same kind of nervous system, a respiratory chamber formed from the fore part of the alimentary canal, and a peculiar organ running along the pharynx which Huxley called the endostyle and which is one of the most striking peculiarities of the whole group. The real nature of the tail was Huxley's most striking discovery. He pointed out that ordinary Ascidians begin life as tiny tadpole-like creatures which swim freely by the aid of a long caudal appendage; and that while these better-known Ascidians lose their tails when theysettle down into adult life, the Appendiculariæ are Ascidians which retain this larval structure throughout life. Von Baer had shown that in the great natural groups of higher animals some forms occur which typify, in their adult condition, the larval state of the higher forms of the group. Thus, among the amphibia, frogs have tails in the larval or tadpole condition; but newts throughout life remain in the larval or tailed condition. Appendicularia he considered to be the lowest form of the Ascidians, and to typify in its adult condition the larval stages of the higher Ascidians.
By this remarkable investigation of the structure of the group of Ascidians, and display of the various grades of organisation, Huxley paved the way for one of the great modern advances in knowledge. When, later on, the idea of evolution was accepted, and zoölogists began hunting out the pedigree of the back-boned animals, it was discovered that Ascidians were modern representatives of an important stage in the ancestry of vertebrate animals, and, therefore, of man himself. There are few more interesting chapters in genealogical zoölogy than those which reveal the relationship between Amphioxus and fish on the one hand, and Ascidians on the other; for fish are vertebrates, and Ascidians, on the old view, are lowly invertebrates. The details of these relationships have been made known to us by the brilliant investigations of several Germans, by Kowalevsky, a Russian, by the Englishmen Ray Lankester and Willey, and by several Americans and Frenchmen. But behind the work of all these lies the pioneer work of Huxley, who first gathered the group of Ascidians together, and in a series of masterly investigations described its typical structure.
Huxley's next great piece of work was embodied in a memoir published in theTransactions of the Royal Societyin 1853, and which remains to the present day a model of luminous description and far-reaching ideas. It was a treatise on the structure of the great group of molluscs, and displays in a striking fashion his method of handling anatomical facts, and deducing from them the great underlying principles of construction. The shell-fish with which he dealt specially were those distinguished as cephalous, because, unlike creatures such as the oyster and mussel, they had something readily comparable with the head of vertebrates. He began by pointing out what problems he hoped to solve. The anatomy of many of the cephalous molluscs was known, but the relation of structures present in one to structures present in another group had not been settled.