THE PLAY OF ANIMALS. 153 



stinct in the exercise of constructive skill by the higher 

 animals, and especially by birds. 



Wallace, in his Philosophy of Birds' Nests, has tried 

 to prove that inherited instinct has very little to do with 

 it. The material, he says, depends on circumstances, 

 and the form partly on natural impulse, but chiefly on 

 imitation. The young bird lives in the nest for days 

 and weeks and learns to know its every detail. Dur- 

 ing the time he is learning to fly he studies the out- 

 side, and naturally keeps a memory picture of the 

 parental home against his own time of need, when he 

 imitates it. The manner of building which has become 

 tradition through imitation, among savage tribes, is thus 

 seen also among the higher animals. 



Worthy of respectful consideration as these opin- 

 ions undoubtedly are, it is extremely probable, to say 

 the least, that Wallace has gone too far. Though here 

 and there imitation may play a more or less important 

 part in this work, it would be hard to dispense with 

 the idea that hereditary impulse is, as a rule, responsi- 

 ble for the constructive skill of animals. The making 

 of a chrysalis by the moth is so unquestionably instinc- 

 tive that no one will deny it, and such facts among the 

 lower orders naturally lead us to consider the case of 

 higher animals analogous. It should be borne in mind, 

 too, that young birds of the kinds that nest but once 

 can not in this way learn the manner of constructing a 

 nest, since the finished one shows little of the process. 

 Weir wrote to Darwin in 1868: " The more I reflect on 

 Mr. Wallace's theory that birds learn to make their 

 nests because they have been themselves reared in one, 

 the less inclined do I feel to agree with him. ... It 

 is usual with many canary fanciers to take out the nest 

 constructed by the parent birds and to put a felt nest 



