Chap. II. THEIR INTELLIGENCE. 97 



it had swallowed a toad lying within a hole, 

 and could not withdraw its head ; the toad 

 was disgorged, and began to crawl away ; it 

 was again swallowed and again disgorged ; 

 and now the snake had learnt by experience, 

 for it seized the toad by one of its legs and 

 drew it out of the hole. The instincts of 

 even the higher animals are often followed 

 in a senseless or purposeless manner : the 

 weaver-bird will perse veringly wind threads 

 through the bars of its cage, as if building a 

 nest : a squirrel will pat nuts on a wooden 

 floor, as if he had just buried them in the 

 ground : a beaver will cut up logs of wood and 

 drag them about, though there is no water to 

 dam up ; and so in many other cases. 



Mr. Romanes, who has specially studied 

 the minds of animals, believes that we can 

 safely infer intelligence, only when we see an 

 individual profiting by its own experience. 

 By this test the cobra showed some intelli- 

 gence ; but this would have been much 

 plainer if on a second occasion he had drawn 

 a toad out of a hole by its leg. The Sphex 

 failed signally in this respect. Now if 

 worms try to drag objects into their burrows 



