630 THE WONDER OF LIFE 



Summer may return the following Spring to the farm- 

 steading which was its birthplace. The question is : 

 Does the return of the swallow differ from the return of a 

 thrown boomerang in kind or only in degree ; that is to 

 say, Does it require different fundamental concepts for its 

 interpretation ? 



We wish to emphasize the fact that the same sort of 

 behaviour requiring historical explanation occurs at 

 all levels of organization, even when there is no question 

 of brains at all. It is distinct from the ' soul and body ' 

 problem. Dr. Driesch, who stands as the foremost pro- 

 tagonist of modern vitalism, got to his strong convictions 

 by experiments on egg-cells, where there are no data as to 

 mental processes. The problem of the autonomy of life 

 would confront us even if to make an impossible assump- 

 tionthere were no animals in the world at all, only plants 

 and us Jack and his bean-stalk, in fact. 



Migration of Eels. As an illustration of the problem 

 of vitalism let us take the migration of eels, which has been 

 recently discussed in this connection in a masterly article by 

 Mr. E. S. Kussell (' Vitalism ', Rivista di Scienza, April, 

 1911). It is a very useful case, because the eel has a brain 

 of a very low order, and we are not warranted in using 

 in regard to it the psychological terms which are indis- 

 pensable in the case of the more intelligent birds and 

 mammals (see p. 458). 



The eels of the whole of Northern Europe probably begin 

 their life below the 500-fathom line on the verge of the deep 

 sea away to the west of the Hebrides and Ireland, and 

 southwards to the Canaries. The early chapters of the 

 life-history remain obscure, but the young larva rises to 

 the upper sunlit waters as a transparent, sideways-flattened, 



