SKIN MARKINGS AND CALLOSITIES OF THE HORSE 497 



uses iii the animal economy, something has to be said in connection with 

 the subject of coloration and skin -markings, of which these curious 

 bodies form an important part. 



SKIN MARKINGS AND CALLOSITIES OF THE HORSE 



Skin Markings. — 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 efiect of colours on the imagination of animals through 

 the eyesight is often marked. Further, Dr. Bonavia shows in numerous 

 illusti'ations 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 whieli 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. 6G3) 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 f;iil to see an excellent pattern for the mark- 

 ing 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 re- 

 tained the most primitive type of coloration clue to the characters of the 

 ancestral armour-plates — a sort of picturation of the carapace after it had 

 been got rid of entirely. 



