SEXUAL VERSUS NATURAL SELECTION 105 



p. 127 that Darwin contemplated the possibility 

 of cryptic colours, such as those of Patagonian 

 animals, being due to Sexual Selection influenced 

 by the aspect of surrounding nature. 



Nearly a year later Darwin in his letter of 

 May 5, 1868?, expressed his agreement with 

 Wallace's views: 'Except that I should put 

 sexual selection as an equal, or perhaps as even 

 a more important agent in giving colour than 

 Natural Selection for protection.' 1 The con- 

 clusion expressed in the above quoted passage is 

 opposed by the extraordinary development of 

 Protective Eesemblance in the immature stages 

 of animals, especially insects. 



It must not be supposed, however, that Darwin 

 ascribed an unimportant role to Cryptic Resem- 

 blances, and as observations accumulated he came 

 to recognize their efficiency in fresh groups of 

 the animal kingdom. Thus he wrote to Wallace 

 May 5, 1867 : * Hackel has recently well shown 

 that the transparency and absence of colour in 

 the lower oceanic animals, belonging to the most 

 different classes, may be well accounted for on 

 the principle of protection.' 2 Darwin also 

 admitted the justice of Professor E. S. Morse's 

 contention that the shells of molluscs are often 

 adaptively coloured. 3 But he looked upon cryptic 

 colouring and also Mimicry as more especially 

 Wallace's departments, and sent to him and to 



1 More Letters, ii. 77, 78. 



2 More Letters, ii. 62. See also Descent of Man (1874), 261. 



3 More Letters, ii. 95. 



