Part 3 (1/2)

CHAPTER V

CREATURES OF THE PAST

Beginning Palaeontological Work--Fossil Amphibia and Reptilia--Ancestry of Birds--Ancestry of the Horse--Imperfect European Series Coical Contemporaneity--Uniformitarianise of the Earth--Interh Huxley took a post connected with Geology only because it was thebefore he became deeply interested not only in the fossils, which at first he despised, but in the general problean by co-operation with Mr Salter in the deterical Survey

Theand describing new species appealed very little to him He had none of the collector's passion for new species; his interest in a creature being not whether or no it was new to science, but what general probley its structure helped to elucidate While he assisted in the routine work of deterical position of the fossils sent in to the ations much farther than the duties of the post required when interesting zoological problems arose His earliest notes ritten in association with his colleague, and consisted of technical descriptions of some small fossils from the Downton Sandstones which were supposed to be fish-shi+elds The peculiarities of structure presented by these aroused his interest, and he began an elaborate series of investigations upon palaeozoic fishes in general Earlier zoologists, such as the great Agassiz, had devoted most of their attention to careful and exact description of the different fossil fishes hich they becaate the relations that existed a the different kinds of structure exhibited in the different fish He laid down the lines upon which future work has been conducted, and, precisely as he did in the case of ators upon lines of research the ends of which have not yet been reached His work upon _Devonian Fishes_, published in 1861, threw an entirely new light upon the affinities of these creatures, and still reh less ireat extinct Crustacea; but, perhaps, his ical as done later, after he had been convinced by Darwin of the fact of evolution In 1855 he had expressed the opinion that the study of fossils was hopeless if one sought in it confirmation of the doctrine of evolution; but five-and-twenty years'

continuous work co the British association at York he declared that ”if zoologists and eists had not put forward the theory, it would have been necessary for palaeontologists to invent it” In three special groups of ani over the gaps between surviving groups of creatures by study of creatures long extinct He began to study the structure of the Labyrinthodonts, a group of extinct monsters which received their name from the peculiar structure of their teeth He published elaborate descriptions of Anthracosaurus from the coal-measures of Northumberland, of Loxomma from the lower carboniferous of Scotland, and of several small forms from the coal- skulls fromentary bones from different localities But in all this work it was the ht which their structure threw upon the structure of each other and of their nearest allies He shewed that these monsters stood on the borderland between fishes, ae of the true structure of these great groups Next, he turned to the extinct reptiles of the Mesozoic age It was generally believed that the Pterodactyls, or flying reptiles, were the nearest allies of birds, but Huxley insisted that the reses were sians adapted to the same purpose About the saland, froroup of extinct reptiles, declared that these were the nearest in structure to birds In association with the upright posture, the iliureat haunch-bone of birds extends far forwards in front of the articulation of the thigh-bone, so that the pelvis in this region has a T-shape, the iliuh-bone the doard lie number of the Dinosaurs had this and other peculiarities of the bird's pelvis, and separated these into a group which he called the ”Ornithoscelida,” seeing in them the closest representatives of the probable reptilian ancestors of birds While further work and the discovery of a still greater number of extinct reptiles has made it less probable that these were the actual ancestors of birds, Huxley's work in this, as in the reat value in itself, but led to a continually increasing series of investigations by others It is not always the pioneer that reatest discoveries in a new country, but the work of the pioneer makes possible and easier the reat piece of palaeontological investigation hich the name of Huxley will always be associated, is the most familiar of all the instances taken from fossils in support of the evolution of aniree of the horse In 1870, in an address delivered to the Geological Society of London, Huxley had shewn that there was a series of anieneralised creature called Anchitheriuested that there were, no doubt, si still further backwards towards the coers and five toes, and went the length of suggesting one or two fossils which ht stand in the direct line of ancestry But in 1876 he visited A the marvellous series of fossils which Professor Marsh had collected from American Tertiary beds Professor Marsh allowed him the freest use of his materials and of his conclusions, and the credit of the final result is to be shared at least equally between Marsh and Huxley The final result was a demonstrative proof of the possible course of evolution of the horse, given in a lecture delivered by Huxley in New York on Sept 22, 1876, and illustrated by drawings from specimens in Marsh's collection The matter of the lecture has beco on evolution, and the treatment is so characteristic of Huxley's brilliant exposition, that it is worth while toquotations from it The lecture was published in the New York papers, and afterwards with other matter formed a volume of _American Addresses_, published by Macmillan, in London

”In most quadrupeds, as in ourselves, the forearm contains distinct bones called the radius and the ulna The corresponding region in the horse seems at first to possess but one bone

Careful observation, however, enables us to distinguish in this bone a part which clearly answers to the upper end of the ulna

This is closely united with the chief mass of the bone which represents the radius, and runs out into a slender shaft which may be traced for some distance doards on the back of the radius, and then in most cases thins out and vanishes It takes still more trouble to make sure of what is nevertheless the fact, that a small part of the lower end of the bone of the horse's forear foal, is really the lower extremity of the ulna

”What is commonly called the knee of a horse is its wrist The 'cannon bone' answers to the middle bone of the five metacarpal bones which support the palm of the hand in ourselves The 'pastern,' 'coronary,' and 'coffin' bones of veterinarians answer to the joints of our ed and thickened nail But, if what lies below the horse's 'knee' thus corresponds to the er in ourselves, what has becoits?

We find in the places of the second and fourth digits only two slender splint-like bones, about two-thirds as long as the cannon bone, which gradually taper to their lower ends and bear no finger joints, or, as they are terristly nodules are to be found at the bases of these two metacarpal splints, and it is probable that these represent rudiits Thus the part of the horse's skeleton which corresponds with that of the huit, and at least two iits; and these answer, respectively, to the third, the second, and the fourth digits inmodifications are found in the hind li contains two distinct bones, a large bone, the tibia, and a smaller and more slender bone, the fibula But, in the horse, the fibula seems, at first, to be reduced to its upper end; a short slender bone united with the tibia and ending in a point below occupying its place

Exa foal's shi+n-bone, however, shews a distinct portion of osseous matter, which is the lower end of the fibula; so that the apparently single lower end of the shi+n-bone is really made up of the coalesced ends of the tibia and fibula, just as the apparently single lower end of the fore-arm bone is composed of the coalesced radius and ulna

”The heel of the horse is the part commonly known as the hock; the hinder cannon bone answers to the middle metatarsal bone of the human foot, the pastern, coronary, and coffin bones, to the middle-toe bones; the hind hoof to the nail, as in the fore foot

And, as in the fore foot, there are merely two splints to represent the second and fourth toes Sometimes a rudi in the sahly complicated and peculiar structure of the teeth of modern horses, Huxley proceeded:

”To anyone who is acquainted with the y of vertebrated animals, these characteristic structures of the horse show that it deviates widely froeneral structure of mammals; and that the horse type is, in eneral mammalian plan The least modified mammals, in fact, have the radius and ulna, the tibia and fibula, distinct and separate They have five distinct and coits is very er than the rest Moreover, in the least enerally forty-four, while in the horse the usual number is forty, and, in the absence of the canines, it may be reduced to thirty-six; the incisor teeth are devoid of the fold seen in those of the horse; the grinders regularly diminish in size from the middle of the series to its front end; while their crowns are short, early attain their full length, and exhibit sis of the horse's grinders

”Hence the general principles of the hypothesis of evolution lead to the conclusion that the horse must have been derived froits on each foot; which had the bones of the forear complete and separate; and which possessed forty-four teeth, arinders had a siradually increased in size from before backwards, at any rate in the anterior part of the series, and had short crowns

”And if the horse had been thus evolved, and the rees of its evolution have been preserved, they ought to present us with a series of forits becoradually take on the equine condition; and the forement of the teeth successively approxi horses

”Let us turn to the facts and see how far they fulfill these requirements of the doctrine of evolution

”In Europe abundant remains of horses are found in the Quaternary and later Tertiary strata as far as the Pliocene formation But these horses, which are so coravel of Europe, are in all essential respects like existing horses, and that is true of all the horses of the later part of the Pliocene epoch But, in the deposits which belong to the earlier Pliocene, and later Miocene epochs, and which occur in Britain, in France, in Germany, in Greece, in India, we find animals which are extremely like horses--which in fact are so siiven in works upon the anatomy of the horse, upon the skeletons of these animals--but which differ in some important particulars

For example, the structure of their fore and hind limbs is somewhat different The bones, which, in the horse are represented by two long splints, i as the middle metacarpal and metatarsal bones; and, attached to the extreeneral character as those of the its are so disposed that they could have had but very little functional importance, and they must have been rather of the nature of the des, such as are to be found in many ruminant animals The _Hipparion_, as the extinct European three-toed horse is called, in fact presents a foot similar to that of the American _Protohippus_ except that in _Hipparion_ the sits are situated further back, and are of smaller proportional size than in the _Protohippus_

”The ulna is slightly th of it, as a very slender shaft, intimately united with the radius, is completely traceable The fibula appears to be in the same condition as in the horse The teeth of the _Hipparion_ are essentially sirinders is in some respects a little more complex, and there is a depression on the face of the skull in front of the orbit, which is not seen in existing horses

”In the earlier Miocene and perhaps in the Eocene deposits of some parts of Europe, another distinct animal has been discovered, which Cuvier, who first described soments of it, considered to be a _Palaeotheriuht on its structure, it was recognised as a distinct genus, under the naeneral characters the skeleton of _Anchitherium_ is very similar to that of the horse, in fact Lartet and De Blainville called it _Palaeotherium equinum_ or _Hippoides_; and De Cristol, in 1847, said that it differed from _Hipparion_ in little ave it the name of _Hipparitherium_ Each foot possesses three coer in proportion to the round in ordinary locomotion The ulna is coh firmly united with the latter

The fibula seeh intimately united with that of the tibia, is clearly united with that of the latter bone There are forty-four teeth; the incisors have no strong pit The canines seem to have been well developed in both sexes The first of the seven grinders, which, as I have said, is frequently absent, and, when it does exist, is sood-sized and perrinder which follows it is but little larger than the hinder ones The crowns of the grinders are short, and, although the fundamental pattern of the horse-tooth is discernible, the front and back ridges are less curved, the accessory pillars are wanting, and the valleys, much shallower, are not filled up with ce his early efforts to trace the descent of the horse froht thrown on the matter from the American discoveries of Professor Marsh: