153 



CHAPTER IV. 



TRACES OF UNITY IN THE PHENOMENA OF 

 INSTINCT. 



MANY instinctive movements are as automatic as the 

 movements of a watch.. The mechanism of the body is 

 constructed so as to "go on" in a certain way, and no 

 other. But the cases of instinctive movement in which 

 many animals act together in concert are not so easily 

 disposed of, and the more they are looked into particu- 

 larly, the more difficult is it to rest satisfied with any 

 elucidation supplied by the. doctrine of automatism. 



The swallow, for example, migrates from England to 

 Africa, and from Africa back again to England with 

 strange regularity. Her movements are ordered so as 

 to avoid frost on the one hand and undue heat on the 

 other. She arrives here about the middle of April 

 and departs about the end of September, when the last 

 of her two broods, like the first, is strong enough to bear 

 the journey. If the last brood be late in making its 

 appearance it runs some risk of being left behind, either 

 to perish outright, or else to hybernate until it is 

 awakened in the spring by the chirp of its returning 

 relatives, but the order of nature seldom goes wrong in 

 this way. And certainly the parents would seem to do 

 all they can to avert such a calamity, by making it 

 their business, for many days before starting, to congre- 

 gate in great numbers and to train their young for the 



