Dr. E. Bonavia, in a recent work entitled Studies in Evolution of Animals, takes a decidedly original view of the nature of the skin markings, such as spots, rosettes, and stripes on the bodies of various mammals. He holds that the action of the nerve-centres has more to do with the remarkable variations of colours and of markings in animals than natural selection has; and there can indeed be no doubt that the nervous system does operate largely in determining colour in some cases, because the fact has been demonstrated. Jacob's device of putting straked rods in view of the flock which he was attending, in order to secure a liberal proportion of straked animals for his own share, was palpably successful, and more recent experience has shown, to the breeder's cost and annoyance, that the determining effect of colours on the imagination of animals through the eyesight is often marked. Further, Dr. Bonavia shows in numerous illustrations how easy it is for spots to be resolved into rosettes and these to be fused together so as to form stripes. A visit to the collection of stuffed animals in the Natural History Museum, London, would make all this quite clear, even to the untrained eye; and an extension of the enquiry to the reptile room might assist in disposing of a good deal of the hesitation which might be felt in accepting Dr. Bonavia's rather startling suggestion that all the markings spoken of, and others yet to be considered, are to be explained by referring them to what he deems to be the real origin of marked mammals - the armour-plated ancestor of the armadillo, of which family the illustration (fig. 663) will afford a good example.

In the figure the reduction of size necessarily disturbs the impression of similarity of markings in the variously spotted mammals and the armadillo, but anyone looking at the huge carapace of an armadillo in the Natural History Museum could hardly fail to see an excellent pattern for the marking of many spotted and speckled creatures.

Dr. Bonavia sums up his views of the nature of coloration of mammals in a few short sentences.

"Glyptodonts, or other armoured mammals," he writes, "were the originals from which all mammals are descended. The jaguar has retained the most primitive type of coloration due to the characters of the ancestral armour-plates - a sort of picturation of the carapace after it had been got rid of entirely.

"All other spotted mammalia, whether marked longitudinally, transversely, or diagonally, are modifications of the jaguar.

" Stripes, whether longitudinal, transverse, or diagonal, arc fusions of lines, of spots, or of rosettes; witness the spotting of certain cheetahs, of certain horses, and of certain tigers with twin stripes."

In the self-coloured mammals, Dr. Bonavia contends, there is evidently a total obliteration of all special markings, though they now and then turn up as atavic or ancestral marks, due perhaps to some atomic change or crossing in the nerve-centres.

Glyptodon reticulatus, restored from the remains exhibited in the Natural History Museum.

Fig. 663. - Glyptodon reticulatus, restored from the remains exhibited in the Natural History Museum.

South Kensington.

Proceeding to the subject of coloration as it affects the horse, the animal which is most immediately under consideration, it is at least very remarkable to observe the curious mixture of colours in roan, piebald, skewbald, grey, and dappled horses - the last term indicating a peculiar pattern irrespective of colour, as the dappling occurs in bay, brown, grey, and dun-coloured horses.

It appears from the experience of breeders that dappled foals are unknown, the peculiar marking appears as the animal gets older; and it must be admitted that in the figures in the accompanying plate (LXVIII) the light spots are singularly suggestive of the plates on the carapace of a large armadillo. In fact, the markings are exactly what would be expected to remain if the armour-plates became loose and ultimately fell off, leaving on the skin only the impression of their outlines.



Photo. by F. Babbage.



The property of Messrs. S. Allsopp & Sons.

Photo by F. Babbage.

No proof of such a change having taken place in the course of ages can be offered, probably none exists, but it may at least be urged that there would be nothing very remarkable in the change, given that the doctrine of evolution is true. On this point Dr. Bonavia remarks that it would be as idle to suppose that the bony plates of the armadillo, the hide plates of the rhinoceros, and the picture plate of the horse are all so like each other by mere accident, as it would be to suggest that the seven cervical vertebras or neck bones, which they possess in common, came to them by chance.

Markings on the face of the horse, before referred to, in the varied forms of the so-called blaze or race, which are always present to a greater or a less extent, varying in size and in colour, can be accounted for on the same principle, as also may similar patches of colour or absence of colour in other parts of the body, round the eyes, on the nose, and on the lower parts of the extremities. And it is also the case that the upper portions of the body are commonly of a darker colour than the under portions. AU these variations, according to Dr. Bonavia, may be explained, if his theory that the horse is descended from an armour-plated ancestor is correct. The lighter colours would indicate the parts from which the armour-plates had first disappeared, leaving only the pictures behind them, and it would naturally happen that the most movable parts, or those most subject to friction, would first get free from the hard plates which, while they protected the parts they covered, would at the same time impair their motion. Thus the eyelids, the limbs, and the terminal extremities would be most likely to be freed earlier than the upper parts of the body, and on the same principle the friction which the abdominal region would suffer, when the animal was lying on the ground, would tend to assist the removal of the armour. The fact of the front of the head being most exposed to rubbing against branches of trees and other projecting bodies would account for loss of armour from that part.

That the process of removal of the armour-plates must have been a gradual one, originated and modified by changes in the conditions of life, cannot be doubted; and, in addition, natural selection, absolutely unchecked by any restraining influences, would inevitably conduce to various alterations in the size and the shape of the picture-markings, exactly as artificial selection does in the present day, with the recognized exceptions which from time to time upset the breeder's calculations through the operation of the law of atavism, or reversion to some ancestral type. It does not, however, at all times occur to the breeder so strongly as it might, that a red calf, or one of any other colour, instead of the expected black one, or a foal with a large white blaze when only a small spot was desired, is not a freak of nature, but the consequence of a sternly enforced law of heredity which never dies, although it may seem to slumber now and again.