92 MIND IN EVOLUTION CHAP. 



tried again, and although the passage was still much too small for 

 convenience, the spider was at length dragged forth, looking 

 much the worse for wear." 1 



Lastly, they think that a P. scelestus actually compared 

 spider and hole before attempting to get the prey in. 



w Presently she went to look at her nest and seemed to be 

 struck with a thought that had already occurred to us that it 

 was decidedly too small to hold the spider. Back she went for 

 another survey of her bulky victim, measured it with her eye, 

 without touching it, drew her conclusions, and at once returned 

 to the nest and began to make it larger. We have several times 

 seen wasps enlarge their holes when a trial had demonstrated 

 that the spider would not go in, but this seemed a remarkably 

 intelligent use of the comparative faculty." 5 



Whatever the correct interpretation of this last obser- 

 vation, enough has been said to show that these wasps 

 adapt means to ends in a way suited to the individual 

 occasion. They are by no means confined to a series of 

 reactions evoked with mechanical uniformity by a uniform 

 stimulus. On the contrary, they are able to deal within 

 limits with each emergency presented by the individual 

 differences of the prey they have captured. Once again, 

 we cannot say that, given a spider and the hole, the 

 <c dragging reflex " is excited. What is excited is the 

 impulse to get it in, and this is accomplished, by dragging, 

 biting, turning over, or enlarging the hole, as the case may 

 be. We are dealing not with reflex action but with the 

 impulse to achieve a particular object to which many 

 muscular actions are subordinated in ways that vary 

 according to the needs of each case. 



Without multiplying instances unnecessarily, we may 

 quote one further statement showing that like birds 3 and 



1 P. 150. 2 P. 158. 



3 A detailed account of nest building, describing in particular the 

 methods of overcoming obstacles is given by Mr. F. H. Herrick,/.^.^. 

 1911, pp. 336-373. He describes a robin bringing strings to his nest, 

 which "brought him up to a short turn by catching on a stub. He at 

 first tried to release them by facing the nest and putting his whole force 

 into a lateral strain. Failing in this he faced around and pulled ; failing 

 again, he advanced and taking up a little of the slack pulled again. I 

 suppose no one would deny that intelligence was displayed in this act, 

 but it should also be noted that his intelligence did not carry him to the 



