no ESSAYS OF A BIOLOGIST 



ory, fear, anger, curiosity, affection, is the simpler 

 and more direct tool, and should be used to supple- 

 ment and make more real the cumbersome and less 

 complete behavioristic terminology, of modification 

 of behaviour, fright, aggression, and the rest. 



It is at least abundantly clear that, if we are to 

 believe in the principle of uniformity at all, we must 

 ascribe emotion to animals as well as to men: the 

 similarity of behaviour is so great that to assert the 

 absence of a whole class of phenomena in one case, 

 its presence in the other, is to make scientific reason- 

 ing a farce. 



"Pas de cerveau — que de I'dme." Those especially 

 who have studied birds will subscribe to this. The 

 variety of their emotions is greater, their intensity 

 more striking, than in four-footed beasts, while their 

 power of modifying behaviour by experience is less, 

 the subjection to instinct more complete. Those 

 who are interested in the details can see from experi- 

 ments, such as those recorded by Mr. Eliot Howard 

 in his Territory in Bird Life, how limited is a 

 bird's power of adjustment; but I will content myself 

 with a single example, one of nature's experiments, 

 recorded by Mr. Chance last year by the aid of the 

 cinematograph — the behaviour of small birds when 

 the routine of their life is upset by the presence of a 

 young Cuckoo in the nest. 



When, after prodi'gious exertions, the unfledged 

 Cuckoo has ejected its foster-brothers and sisters 

 frorn their home, it sometimes happens that one of 



