HOLMES'S THE EVOLUTION OF ANIMAL INTELLIGENCE 451 



conclusions from them. We must not forget, as certain psycho- 

 logical trainers of animals have done, that "the lion of the 

 desert is quite a different creature from the lion of the circus." 

 Holmes discusses the formation of ideas, reasoning, and imita- 

 tion in the higher animals, and reports the exploits of the monkey 

 Peter, whom an illustration shows in the act of dining. He 

 brings the book to a close without formulating his conclusions, 

 but they are apparent as one reads it. 



Some surprise may be felt that Holmes fails to mention the 

 work of Pawlow's school, which deals with conditioned reflexes 

 where the method of psychic salivation is used. These experi- 

 ments, which furnished the stimulus for the recent researches 

 of Metalnikow on the infusoria, have the great advantage of 

 helping us to penetrate into the determinism of animal behavior, 

 and making us understand how far such behavior is from being 

 adaptive. In my opinion, Holmes lays too much stress on 

 adaptation, the finality of acts : in most cases this is but a delu- 

 sion and a snare. Intelligence itself is for us only a very im- 

 perfect instrument. 



However, Holmes's book is very valuable ; its facts are well 

 selected, its ideas interesting and original. Every biologist and 

 philosopher should read it. 



