Birds and Reptiles.

All subsequent research has also tended in this direction; and at the present day the investigations of such men as Riitemeyer and Gaudry have tended to fill up and connect, more and more, the gaps in our existing series of mammals. But I think it may have an especial interest if—instead of dealing with these cases, which would require a great deal of tedious osteological detail to explain—if I take the ease of birds and reptiles—which groups, at the present day, are so clearly distinguished from one another that there are perhaps no classes of animals which in popular apprehension are more completely separated. Birds, as you are aware, are covered with feathers; they arc provided with wings; they are specially and peculiarly modified as to their anterior extremities; and they walk perpendicularly upon two legs; and those limbs, when they are considered anotomically, present a great number of exceedingly remarkable peculiarities, to which I may have occasion to advert incidentally as I go on, but which are not met with even approximately in the existing form of reptiles. On the other hand, reptiles, if they have a covering at all, have a covering of scales of bony plates. They possess no wings; they are not volatile, and they have no such modification of the limbs as we find in birds. It is impossible to imagine any two groups apparently more definitely and distinctly separated. As we trace the history of birds back in time, we find their remains abundant in the tertiary rocks throughout their whole extent; but, so far as anything is known, birds of the tertiary rocks, though retaining the same essential character as the birds of the present day—that is to say, the tertiary bird coming within the definition of our existing birds—are as much separated from reptiles as our existing birds are. A few years ago no remains of birds had been found below the tertiary rocks, and I am not sure but that some persons were prepared to demonstrate that they could not have existed at an earlier period. But in the last few years such remains have been discovered in England, though unfortunately in a very imperfect condition. In your country the development of cretaceous rocks is enormous, and the conditions under which the later cretaceous strata have been deposited are favorable for the preservation of organic remains in a perfect condition, and the researches full of labour and toil which have been carried on by Professor Marsh in these Western cretaceous rocks have rewarded him with the discovery of forms of birds of which we have hitherto no conception. By his kindness, I am enabled to place before you a restoration of one of page 23 these extraordinary birds, every part of which can be thoroughly proved and justified. The remains exist in the greatest beauty in his collection.

A bird about six feet high, a large bird, existed during the later cretaceous epoch, and which in a great many respects is astonishingly like an existing diver or grebe, so like it indeed, that had this skeleton been found in a museum, I suppose—if the head had not been known—it would have been placed in the same general group as the divers and grebes of the present day. But this bird differs from all existing birds, and so far resembles reptiles in the one important particular that it is provided with teeth. These long jaws (referring to the picture behind him) are beset with teeth, as in this diagram. Here is one of the teeth, and in this particular it differs entirely from any existing bird, and it is in view of the characteristics of this Hesperornis that we are obliged to modify the definition of the classes of birds and reptiles. Before the production of a creature such as this, it might have been said that a bird had such and such characteristics, among which were an absence of teeth, but the discovery of a bird that had teeth shows at once that there were ancient birds that in that particular respect approached reptiles more nearly than any existing bird does.

The same rocks have yielded another bird (Ichthyornis) which also has teeth in its jaws, the teeth in this case being situated in distinct sockets, while those of the swimming bird (Hesperornis) differ essentially, being in grooves. The latter also had page 24 smaller wings than those of a flying bird. Ichthyornis also differed in the fact that the joints of its backbone—its vertebne—had not the peculiar character that existing birds have, but were concave at each end. This discovery leads us to make another modification in the character of the divisions of birds, showing that they are not so far off from reptiles. We know nothing whatever of birds older than these until we come down to the Jurassic period, and from that period we know a single bird which was first made known by the finding of a fossil feather. It was thought wonderful that such a perishable thing as a feather should be discovered and nothing more, and so it was, and for a long time nothing was known of this bird except its feather. But by and by one solitary specimen was discovered, which is now in the British Museum. That solitary specimen is unfortunately devoid of its head, but there is this wonderful peculiarity about the creature, that while so far as its feet are known it has all the characters of a bird, all those peculiarities by which a bird is distinguished from a reptile, when we examine the vertebral column, it is unlike a bird and like a reptile. It had a long tail with a fringe of feathers on each side. We find that division of the wing which corresponds with the band, and the wing itself differing in some very remarkable respects from the structure it presents in a true bird. In a true bird the wing answers to these three fingers—the thumb and next two fingers of my hand—and these bones behind the fingers which I am touching are all fused together in one mass—anchylosed, or coossified, as we say—and the whole apparatus except the thumb is bound up in a great sheath of integument, which supports the feathers of the wing; the edge of the arm, &c., carrying the feathers. It is in that way that the bird's wing becomes an instrument of flight. In this bird—the Archaeopteryx—the upper arm is like that of a bird; these two fore-arm bones are more or less like that of a bird, but these fingers are not bound together—they are free, and they are all terminated by strong claws not like a bird, but evidently by such a structure as reptiles possess, so that in this single Archaeopteryx you have an animal which becomes to a certain extent the midway place between a bird and a reptile. It is a bird so far as its hand and limbs are concerned—it is essentially and thoroughly a bird in the fact that it possesses feathers, but it is much more properly a reptile, in the tact that its anterior limb has separate bones resembling the fore-limb of a reptile. All these cases, so far as they go, you will observe, are in favour of Evolution to this extent, that they show that in former periods of the world's history there were creatures existing which overstep the bounds of all existing classes and groups, and tend to fill up the intervals which at present exist between them. But we can go further than this. It is possible to fill up the interval between birds and reptiles in a much more striking manner. I don't say that this is to be done by looking upon what are called the Pterodactyls as the intermediate form between birds and reptiles. Throughout the whole series of the mesozoic rocks we meet with some exceedingly remarkable flying creatures, some of which attain a great size, their wings having a span of eighteen or twenty feet or more, and these are known as Pterosauria, or Pterodactyls. We find these with a bird-like head and neck, with a vertebral column sometimes terminated in a short tail, and sometimes in a long tail, and in which the bones of the skeleton present one of the peculiarities which we often consider are most characteristic of birds—that of being excavated and filled with h air, or having pneumatic cavities, which make the creature specifically light in its flight.

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Like a bird, this creature has a largish breast-bone, with a crest upon it and a shoulder-girdle much like a bird; but from that point onward, so far as I can see, special, particular resemblances end, and a careful examination of the fore-limbs shows you that they are not bird's wings; they are something totally different from a bird's wings. And then, again (pointing to chart), those are not a bird's posterior extremities, but are rather what is termed reptilian. You will observe that the fore-arm presents nothing that I need dwell upon, but the bones of the hand are very wonderful. There are four fingers represented. These four fingers are large, and three of them, these, which answer to these three in my hands, are terminated by claws, while the fourth is enormously prolonged into a great jointed style. Nothing could be more unlike a bird's claw than this is. You see at once from what I have stated about a bird's wing that there could be nothing more unlike a bird's wing than this is. It was concluded by general reasoning that this finger was made to support a great web like a bat's wing. Specimens now exist showing that this was really the case, that this creature was devoid of feathers, but the fingers supported a vast web like a bat's wing. We see this ancient reptile floated by a similar method, so that the Pterodactyl, although it is a flying reptile, although it presents some points of similarity to birds, yet is so different from them that I do not think that we have any right to regard it as one of the forms intermediate between the reptile and the bird.