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- 

 tion — there 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. Eussell (' 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 hne 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, 



