34 THE PLAY OP ANIMALS. 



It is generally asserted that birds would build nests 

 like all others of their kind even if they had never seen 

 them. That would undeniably be instinctive. " This 

 point, although so important to the question at issue, is 

 always assumed without proof, or even against proof, 

 for the known facts are opposed to it. Birds brought 

 up from the egg in cages do not make the character- 

 istic nest of their species, even though the proper ma- 

 terials are supplied them, and often make no nest 

 at all, but rudely heap together a quantity of ma- 

 terials." 



" With regard to the song of birds, moreover, which 

 is thought to be equally instinctive, the experiment has 

 been tried, and it is found that young birds never have 

 the song peculiar to their species if they have not heard 

 it, whereas they acquire very easily the song of almost 

 any other bird with which they are associated." For 

 AVallace, such cases are accounted for by simple imita- 

 tion and in a slight degree by adaptation of the indi- 

 vidual to new conditions.f However, he does not con- 

 sider it impossible that the existence of pure instinct 

 may be proved in some cases. J 



Later, Wallace changed his view entirely, and ad- 

 mitted inherited instinct. " Much of the mystery of 

 instinct arises from the persistent refusal to recognise 

 the agency of imitation, memory, observation, and rea- 

 son as often forming part of it "; but with these ele- 

 ments depending on individual effort, he recognises the 

 force of inheritance as one of the actual elements of 



* Loc. cit, p. 220. This shows the building tendency in spite of 

 the abnormal conditions ! 



f His grounds bring to mind in part those of Condillac and 

 Leroy. 



X Loc. cit., p. 230. 



