Characters as Adaptive and Specific. 213 



mixia be suggested in explanation of the discharge 

 of colouring in cave-faunas, the continuance of colour 

 in deep-sea faunas appears to show the explanation 

 insufficient. Thirdly, according to my view of the 

 action of panmixia as previously explained, no total 

 discharge of colouration is likely to be caused by such 

 action alone. At most the bleaching as a result 

 of the mere withdrawal of selection would proceed 

 only to some comparatively small extent. Fourthly, 

 Mr. Packard in the elaborate Memoir on Cave 

 Fauna, already alluded to, states that in some of 

 the cases the phenomena of bleaching appear to have 

 been induced within very recent times if not, indeed, 

 within the limits of a single generation. Should 

 the evidence in support of this opinion prove trust- 

 worthy, of course in itself it disposes of any sugges- 

 tion either of the presence or the- absence of natural 

 selection as concerned in the process. 



Nevertheless, I myself think it inevitable that to 

 some extent the cessation of selection must have 

 helped in discharging the colour of cave faunas ; 

 although for the reasons now given it appears to me 

 that the main causes of change must have been of 

 that direct order which we understand by the term 

 climatic. 



As regards dogs, the Rev. E. Everest found it impos- 

 sible to breed Scotch setters in India true to their type. 

 Even in the second generation no single young dog 

 resembled its parents either in form or shape. " Their 

 nostrils were more contracted, their noses more pointed, 

 their size inferior, and their limbs more slender 1 ." 

 Similarly on the coast of New Guinea, Bowman says 



1 Variation, &c. vol. i. p. 40. 



