278 Colour and the Struggle for Life 



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 

 conclusion expressed in the above quoted passage is opposed by 

 the extraordinary development of Protective Resemblance in the 

 immature stages of animals, especially insects. 



It must not be supposed, however, that Darwin ascribed an 

 unimportant role to Cryptic Resemblances, and as observations 

 accumulated he came to recognise 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 con- 

 tention 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 Professor 

 Meldola observations and notes bearing upon these subjects. Thus 

 the following letter given to me by Dr A. R. Wallace and now, by kind 

 permission, published for the first time, accompanied a photograph 

 of the chrysalis of Papilio sarpedon choredon, Feld., suspended from 

 a leaf of its food-plant : 



July 9f/<, 

 DOWN, 



BECKENHAM, KENT. 



MY DEAR WALLACE, 



Dr G. Krefft has sent me the enclosed from Sydney. A 

 nurseryman saw a caterpillar feeding on a plant and covered the 

 whole up, but when he searched for the cocoon [pupa], was long 

 before he could find it, so good was its imitation in colour and form 

 to the leaf to which it was attached. I hope that the world goes well 

 with you. Do not trouble yourself by acknowledging this. 



Ever yours, 



CH. DARWIN. 



Another deeply interesting letter of Darwin's, bearing upon pro- 

 tective resemblance, has only recently been shown to me by my friend 

 Professor E. B. Wilson, the great American Cytologist. With his kind 



1 More Letters, u. pp. 77, 78. 



- More Letters, n. p. 62. See also Descent of Man, p. 261. 



3 More Letters, n. p. 95. 



