VI DEFENCES OF INSECTS 241 



colour. Some authorities have believed that we find 

 in colour a result attributable to the direct influence 

 of surroundings accumulated through heredity. The 

 preceding experiments on Variable Protective Re- 

 semblance showed the medium of the nervous system 

 to be indispensable, so that the results are indirect. 



It must not be thought, however, that variable 

 protective resemblance is yet in part due " to the 

 accumulation through heredity of the indirect influence 

 of environment working by means of the nervous 

 system." J The power of adjustment of colour pos- 

 sessed by each insect is essentially adaptive. Bias to 

 particular colour through the influence of ancestors 

 would at once weaken the efficacy of the property, 

 inasmuch as different individuals are likely to meet 

 with different environments. But here also, as in all 

 other cases, the power is to be explained by the 

 operation of natural selection. The primary varia- 

 tions are controlled and quickened by it. Its function 

 is to take advantage of a faculty, regardless of the 

 manner in which it originates and at what period of 

 the insect's life the change is induced. The power of 

 changing colour is beneficial to the insects that pos- 

 sess it, this few naturalists will deny. It follows 

 that natural selection will produce and maintain 

 the power, that it will eliminate any variations, or, 

 to express it differently, that it will eliminate indi- 

 viduals which tend to depart from this useful 

 capacity. 



1 Poulton. 



R 



