DARWIN AND BERGSON ON EVOLUTION 



reasons : first, a chrysalis is incapable of learning by experience 

 how to improve anything — even more obviously incapable of 

 learning concerning a structure which it never makes. Secondly, 

 however intelligent a chrysalis may be, the experience is of such 

 a nature that its stores of learning cannot be handed down to 

 posterity." * 



The whole of this argument is equally destructive of Bergson's 

 hypothesis. How can an unconscious insight into life confer on an 

 insect the gift of prophecy and enable it to prepare in advance 

 against the attacks of enemies it will never see — enemies that were 

 never met by any of its ancestors ? For the chrysalis detected by 

 one of its natural foes is at once deprived of the possibility of 

 becoming an ancestor. 



No reasonable interpretation of these facts has ever been offered 

 except the natural selection of Darwin and Wallace. In the light 

 of this hypothesis we cannot but regard " these beautifully adapted 

 structures as the outcome of countless generations during which 

 the attacks of enemies have been, on the whole, more successful 

 against the products of less perfected instincts and less so against 

 those of the more perfected." f 



It may be urged that the instinct of cocoon-making is not so 

 remarkable or so difficult to explain as that which impels the Ammo- 

 phila to sting its prey. It is very doubtful whether this contention 

 is sound. Certainly the cocoon-making instinct is the more fixed 

 and complete ; for Dr. and Mrs. Peckham have shown that there 

 is great variability and uncertainty in the methods of the Ammofhila 

 and in the effects produced on its victim. 



It may be of interest to show by an example the elaborate com- 

 plexity of which the cocoon-making instinct is capable. I select the 

 cocoon (B, C) of the day-flying West African moth (Deilemera antinorii) 

 (A), recently investigated by Mr. W. A. Lamborn in the Lagos 

 district. The cocoon itself is slight and in large part concealed by 

 a heaped-up mass of yellowish spheres fixed to the outermost layers 

 of silk. When Mr. Lamborn first saw the two cocoons shown at 

 B and C he quite believed that his caterpillars had been parasitised, 

 and was greatly surprised when the moth (A) emerged from one of 

 them (C). Even then he watched the cocoon for a long time, half 

 expecting that some minute insect would emerge from the small 



* L. c, pp. 157, 159. t L. c, p. 160. 



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