148 STUDIES IN THE EVOLUTION OF ANIMALS 



similar markings, but the black on its back is less marked. Very 

 probably, either the one or the other has given our black and tan 

 domestic Dogs their distinctive coloration, which, in some varieties, 

 becomes tan and white. These and many others, in my opinion, 

 owe that particular feature to an ancestral carapace, although the 

 separate spots — vestiges of bone-rosettes — may have wholly dis- 

 appeared ; they still persist, however, in the Dalmatian breed of 

 Dogs. 



I have seen a curiously marked Toy Terrier of the black-and-tan 

 breed. Its back was grey and sharply defined like that of a Badger, 

 and it was blotched and striped with black. And in the Natural 

 History Museum there is a tiny Cheetah from the Cape which is 

 also curiously marked. Its back is grey like that of a Badger, and 

 the other parts are spotted. It is impossible to contemplate these 

 reversions without -thinking that they must have a deeper meaning 

 than that of being simply accidental. 



At the risk of wearying the reader with repetitions, let us now 

 try to recapitulate briefly the whole process, and endeavour to form 

 a clear conception of how these phenomena could have been 

 brought about. 



First, we must assume that natural selection, as indeed is 

 admitted by modern biologists, must have had a great deal to do 

 with evolving, from previous rriodes of armour, with the help of 

 congenital variations, the forms of carapaces we see in the Glypto- 

 donts and Armadillos with plate-rosettes. The congenital varia- 

 tions in the plates of carapaces were presumably brought about 

 by changes in the central nerve-action. This action we as yet do 

 not understand, any more than we understand how thought is 

 evolved from it. There can be no doubt however that in the 

 higher animals it is all-important, and governs everything. 



This original nerve-action, however caused, by which a resetted 



