84 MIND IN EVOLUTION CHAP. 



metamorphosis ; and he found that if he took a caterpillar which 

 had completed its hammock up to, say, the sixth stage of con- 

 struction, and put it into a hammock completed up only to the 

 third stage, the caterpillar did not seem puzzled, but repeated the 

 fourth, fifth, and sixth stages of construction. If, however, a 

 caterpillar was taken out of a hammock made up, for instance, to 

 the third stage, and put into one finished to the ninth stage, so 

 that much of its work was done for it, far from feeling the benefit 

 of this, it was much embarrassed, and even forced to go over the 

 already finished work, starting from the third stage which it had 

 left off before it could complete its hammock. So, again, the hive- 

 bee in the construction of its comb seems compelled to follow an 

 invariable order of work." l 



We have here a case of the mechanical type approaching 

 if it does not touch the boundary of the compound reflex, 

 while in the other illustrations from caterpillar life we had 

 instances of the adaptive, plastic type. 



The power of overcoming obstacles, and also the 

 limitation of that power as long as we move in the region 

 of pure instinct, is well illustrated by another " caterpillar 

 story " communicated to Mr. Romanes by Mr. G. B. 

 Buckton : 



" Many caterpillars of Pieris rapce have, during this autumn, 

 fed below my windows. On searching for suitable positions for 

 passing into chrysalides, some eight or ten individuals, in their 

 direct march upwards, encountered the plate-glass panes of my 

 windows ; on these they appeared to be unable to stand. Accord- 

 ingly in every case they made silken ladders, some of them five 

 feet long, each ladder being formed of a single continuous thread 

 woven in elegant loops from side to side. . . . The reasoning, 

 however, seems to be but narrow, for one ladder was constructed 

 parallel to the window-frame for nearly three feet, on which 

 secure footing could be had by simply diverting the track two 

 inches." 2 



The larva has, it would seem, a definite method of deal- 

 ing with the particular difficulty of a smooth surface. It 

 does not matter that a much simpler method is at hand. 

 The caterpillar acts more majorum, and would doubtless be 

 shocked at the suggestion that it should depart from 

 tradition. This suggestion, however, its perceptions are 

 incapable of making to it. Lastly, we may take a case 

 1 ME. A. p. 179. 2 Romanes, p. 236. 



