TRACHEATES 19 I 



While natural selection thus enables us to understand 

 the origin of protective colouring, we can see no 

 application in this case of the Lamarckian principle. 

 The protective colours of animals cannot possibly have 

 been raised to their present condition by continuous use 

 and inheritance of the results. In the first place, it is 

 impossible for an animal to become green because it 

 takes to sitting on leaves ; and in the second place, 

 even if the animal knew that it would be an advantage 

 to be green, it could not change its colour by an effort 

 of will. It has been stated that the light causes the 

 colours, and that the animal's skin photographs the 

 surroundings, to some extent. It is striking, for 

 instance, that in many day-butterflies, which draw the 

 fore-wings between the upward-folded hind wings when 

 they rest, so that only the tips of the fore-wings can be 

 seen, these are only protectively coloured like the back 

 wings just to that extent, while the unseen part of them 

 is often very lightly coloured. Thus the back wings 

 and the tips of the front wings have exactly the same 

 colour-design. And the colouring of the tips of the 

 front wings is more or less extensive according to the 

 habit of drawing the wings in more or less thoroughly. 

 We find this difference in such apparently similar 

 butterflies as the large and small tortoise-shells. But in 

 the butterflies that do not draw in their front wings the 

 whole surface is protectively coloured. 



If, however, it seems on superficial inquiry that the 

 light may have produced the colours, and was only able 

 to do this on the exposed parts of the wings, we shall 

 be compelled to abandon the hypothesis on further 



