THE COMMON-SENSE VIEW 191 



their nests — a very remarkable act of intelligence, 

 since the use of tools is not common even among 

 the higher mammals (13). Fishes have been 

 taught to assemble at the ringing of a bell, and 

 toads and tortoises to come at the call of their 

 favourite friends. An alligator which was kept 

 tame for several years became so much attached 

 to its master that ' it followed him about the 

 house like a dog, scrambling up the stairs after 

 him, and showing much affection and docility.' 

 The favourite friend and companion of this 

 alligator was the cat ; and, whenever the cat 

 stretched herself on the floor in front of the fire, 

 the alligator would lie down beside her, with its 

 head on the cat, and go to sleep. * When the cat 

 was absent, the alligator was restless, but it always 

 appeared happy when the cat was near it ' (12). 



Wolves and foxes sometimes cooperate with 

 each other in their hunting expeditions, somewhat 

 as men do in theirs. One of their number will 

 crouch in ambush by the side of a road known to 

 be used by hares or other small animals, and leap 

 on the unsuspecting fugitives when driven that 

 way by others of the hunting band. Many animals 

 post sentinels when they eat or sleep or engage in 

 other hazardous undertakings, and these sentinels 

 show a good deal of discrimination in distinguish- 

 ing between animals that are friendly and those 

 that are not. Beavers not only build lodges to 

 live in, but also construct dams to keep the water 

 in which the villages are located at a certain height. 

 The outlet of these dams is carefully regulated, 



