he-His Own Contributions to the Theory-The Classification of Birds-Huxley Treats them

s Huxley began his scientific work as a medical student, the groundwork of all his knowledge was study of the anatomy and physiology of man. Moreover, throughout the greater part of his working life, he had more to do with the extinct forms of life. The vertebrate animals, from the great facility for preservation which their hard skeleton presents, as well as from the extremely important anatomical characters of the skeleton, bulk more l

ws and summary of the views of others form the basis of our modern knowledge. This work was put before the public in the course of a series of lectures on Comparative Anatomy g

pansion of the spinal cord in the region of the anterior limbs and an expansion in the region of the hind limbs, the latter indeed having recently been shown in some extinct creatures to surpass the brain in size. In a similar simple fashion the skull may be taken as an expanded anterior part of the vertebral column, serving as an expanded box for the brain, just as in the regions of the pectoral and pelvic expansions of the cord there are similar expansions of the surrounding bony case. We know now, from greater knowl

sheep's skull, in which the apparent vertebral structure was very obvious, as, indeed, anyone may see at a glance. It was in 1820, long after the theory had been made current, that the poet first publicly narrated that in a similar way he had long before come to the same conclusion; but Huxley was able to show that, although announcing it later, Goethe had in reality anticipated the anatomist. A passage occurs in a letter to a friend, of a date in 1790, which admits of no doubt. "By the oddest happy chance, my servant picked up a bit of an animal's skul

y nerves passed; a jaw vertebra, in the sphenoidal region, through which the nerves to the jaws passed; an eye vertebra in front, pierced by the optic nerves, and again in front a nose vertebra, the existence of which he doubted at first. Quite rightly, he discriminated between the ordinary bones of the skull and the special structures surrounding the inner ear which he declared to be additions derived from another source. So far it cannot be doubted that the vertebral theory made a distinct advance in our knowledge of the skull. It was to a certain extent, however, thrown into disrepute by various fantastic theories with which Oken surrounded it. Later on, Cuvier

d. These were essentially identical with the centra of the four vertebr? of Oken. Similarly, he showed the composition of the lateral and dorsal walls, proving the essential identity of the structures involved and of their relations to the nerve exits in the great types he had chosen. In the series of lectures delivered before the College of Surgeons, he extended his observations to a much larger series of vertebrates, and substantially laid down the main lines of our knowledge of the skull. In two important respects his statements were not merely a codification of existing

e different from those of the vertebral column. The notochord alone is common to both. The skull is built up of longitudinal cartilaginous pieces, now known as the "parachordals" and "trabecul?," of sense capsules enclosing the nose and ear, and of various roofing bones. In the historical development of the skull three grades become apparent; a primitive stage, as seen in Amphioxus, where there is nothing but a fibrous investment of the nervous structures; a cartilaginous grade, as seen in the skate or shark, where the skull is formed of cartilage, very imperfectly hardened by earthy deposits; a bony stage, seen in most of the higher animals. He shewed that in actual development of the higher animals these historical grades are repeated, the skull being at first a mere membranous or fibrous investment of the developing nervous masses, then becoming cartilaginous, and, lastly, bony. He made some important prophetic remarks as to the probable importance that future embryological work would give to the distinction between cartilage and membrane bones-a prophecy that has been more than fully realised by the investigations of Hertwig and of others. Our present knowledge of the skull differs from Huxley's conception practically only in a fuller knowledge of details. We

pted by zo?logists. Before Huxley, it had been attempted by a number of distinguished zo?logists; but, for the most part, these had relied too much on merely external characters and on superficial modifications in obvious relation to habits. When Huxley, in the course of a set of lectures on Comparative Anatomy, was about to approach the subject of birds he was asked by a zo?logist how he proposed to treat them. "I intend," he replied, "to treat them as extinct animals." By that he meant that it was his purpose to make a prolonged study of their skeletal structures the basis of his grouping, following the lines which Cuvier, Owen, and he himself had pursued so successfully in the case of the fossil remains of vertebrates. The result was that this first systematic study of even one set of the anatomical characters of the group completely reformed the method by which all subsequent workers have tried to grapple with the problem; ornithology was raised from a process akin to stamp-collecting to a reasoned scientific study. The immedi

pe, of the tendons of the feet, and many other structures which display anatomical modifications in different birds. The modern student finds that all these new sets of facts are much greater in bulk than the work of Huxley, and it is easy for him to remain in ignorance that they were all suggested and inspired by the method which Huxley employed. He finds that further

lished in the Journal of the Linn?an Society of London. It was known in a general way that different kinds of creatures were found in different parts of the world, but little attempt had been made to map out the world into regions characterised by their animal and vege

far wrong in supposing them to have been the result of distinct creations. Assuming, then, that there are, or may be, more areas of creation than one, the question naturally arises

Pal?arctic, Ethiopian, Indian, and Australian, and his answer, with minor altera

spersal, of similarities due to common descent, and of the modifying results produced by isolation. He gave, in fact, a theory of the "creations" which Mr. Sclater had shewn to be a probable assumption. It was in the nature of things that Huxley should make a contribution to a set of problems so novel and of so much importance to zo?logy. In 1868, in the course of a memoir on the anatomy of the gallinaceous birds and their allies, he made a useful attempt, nearly the first of its kind, to correlate anatomical facts with geographi

has not been generally accepted as a modification of Mr. Sclater's scheme, it called attention in a striking fashion to some very remarkable features in the distribution of animals. Subsequent writers have considerably extended Huxley's conception of the similarities to be found among the more southern land areas. They have pointed out that the most striking idea of the distribution of land and water on the surface of the globe is to be got by considering the globe alternately from one pole and from the other. In the south, a clump of ice-bound land, well within the Antarctic Circle, surrounds the pole. All else is a wide domain of ocean broken only where tapering and isolated tongues of land, South America, the Cape, Australia, lean down from the great land masses of the north. On the other hand, all the great land masses expand in the Northern Hemisphere, and shoulder one another round the North Pole. America is separated from Asia only by the shallowest and narrowest of straits; an elevation of a few fathoms would unite Greenland with Europe. Science points definitely to some part of the great northern land area as the centre of life for at least the larger terrestrial forms o

f Australia and of South America of a kind which makes the existence of a direct land connection in the Southern Hemisphere extremely probable. Moreover, Ameghino has recently described some marsupial fossils from South America which, he states, belong to the Australian group of Dasyurid?, and Oldfield Thom

olar region for the Northern Hemisphere, and by elevating New Zealand into a separate regio

ect of Huxley's first published contribution to scientific knowledge), he added to the number of known facts, he did even more important work in co-ordinating and grouping together the known body of facts. To him are due not only the names, but the idea, that the mammalian animals fall into three grades of ascending complexity of organisation: the reptile-like Prototheria, which lay large eggs, and which have many other reptilian characters; the Metatheria, or m

nte