io8 ESSAYS OF A BIOLOGIST 



its presence in the other, is to make scientific reasoning 

 a farce. 



' Pas de cerveau — que de Fame,'* 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 this 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 prodigious exertions, the unfledged 

 Cuckoo has ejected its foster-brothers and sisters from 

 their home, it sometimes happens that one of them 

 is caught on or close to the rim of the nest. One 

 such case was recorded by Mr. Chance's camera. 

 The unfortunate fledgling scrambled about on the 

 branches below the nest ; the parent Pipit flew back 

 with food ; the cries and open mouth of the ejected 

 bird attracted attention, and it was fed ; and the 

 mother then settled down upon the nest as if all was 

 in normal order. Meanwhile, the movements of 

 the fledgling in the foreground grew feebler, and one 



