DIC SIGN LV THE O KG AX 1C WORLD. 443 



the colour of the progeny ; and this belief seems justified by 

 modern observation. Thus, the Dingo, or wild dog of Australia 

 (probably the descendant of some domesticated race originally 

 introduced thither by man), has a uniform dull brown hue; but 

 when the parents have been brought by domestication into a more 

 varied environment, the pups vary in colour, as has been often 

 seen in the Zoological Gardens. The breeders of the polled 

 Angus a particular race of black cattle in Scotland who make 

 a great point of keeping up the perfect uniformity of their black- 

 IKSS, getting rid of every individual that has even a single white 

 foot take care to have everything black about their farmsteads ; 

 all the buildings are black, the horses are black, the dogs are 

 black, the fowls are black. No breeder will have anything 

 coloured or white about his place. Though no account can be 

 given of the physiological action which makes these precautions 

 effective (as they are asserted to be) in securing the desired result, 

 yet I am strongly inclined to think that some influence of this 

 kind is concerned in producing many singular correspondences 

 between the surface aspect of Fishes and Crustacea inhabiting 

 shallow waters, and the characters of the bottoms on which they 

 live. Every angler for trout is familiar with variations of this 

 kind ; and I have bcjn assured of cases in which these fish, when 

 transferred from one pa.t of a stream to another, were found in 

 no long time to have undergone a change in surface-markings, 

 which gave them the same conformity to the new bottom as they 

 previously had to the old. I once found in a pool on the sea 

 shore some small Fishes and shrimp-like Crustaceans, the hue of 

 whose surface so exactly resembled that of the yellow sand 

 speckled with black that formed the bottom and sides of the pool, 

 that the closest watching scarcely enabled me to distinguish them ; 

 and I found, on microscopic examination of their respective in- 

 ti/gunients, that their coloration was due in both alike to the 

 presence of large yellow pigment-cells, with snull black ones 

 interspersed. Hence, even if we attribute this singularly close 

 adaptation to &quot;natural selection,&quot; we have just as much to account 

 for the development of the peculiar pigmentation in the variety- 

 alike of the 1-ish and of the Crustacean that exhibited it, as if we 

 believed these animals to have been originally created with it, 



