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soft-shelled " turtles " are placed over the very centre of 

 the body. True, this is protected by a shell, but this is 

 easily pierced when the animal is young. We know so little, 

 however, of the life-history of these creatures, that it may 

 well prove, after all, that these spots, so conspicuous in 

 museum specimens, or when the animal is newly dragged 

 out of the water, are highly protective in character, 

 harmonising, perhaps, with the stones or vegetation of the 

 under-world in which these creatures live. 



While there can be no doubt as to the facts in regard to 

 the phases of coloration just discussed, the interpretation 

 placed thereon is obviously theoretical, and therefore 

 liable to be set aside at any time. Indeed, there are not 

 wanting those at the present day who venture to call this 

 interpretation in question. These objectors, however, have 

 so far given us nothing better than sceptical criticism, 

 and much of it not of a very convincing kind. In any 

 speculations on this theme certain underlying aspects of 

 the subject are commonly ignored, which, nevertheless, 

 must always be borne in mind when seelcing to piece 

 together the evidence which we have just reviewed. 



In all endeavours to explain the origin of this striped 

 coloration, and the further evolution therefrom of spots, 

 mottlingSj transverse bars, ocelli, and so on, stress has been 

 laid, and rightly, on the tendency of all animals to vary 

 in all directions, and in colour perhaps especially. But 

 one must go deeper : one must begin with the question, 

 Whence the origin of the pigments which display these 

 variations f There can be little doubt but that these are 

 waste products of the blood deposited in the skin or its 

 covering, and retained there because their presence confers 

 a benefit." But the further elaboration of the different 

 kinds of pigment, and of structural colours, which are not: 



