Einier on G7^owtJi and Inheritance /^2>7 



no more supported by facts than some other propositions of 

 his, and to rest, in fact, upon nothing but assumptions con- 

 cerning mere possibiUties. To us, however, it appears clear 

 that every one of the various hypotheses hitherto proposed 

 is manifestly insufficient to account for the facts. For 

 Kolliker's theory, as for Eimer's, Weismann's, and Nageli's, 

 there is required, besides some actual evidence, a further 

 intellectual conception to make it even thinkable — a matter 

 we shall have occasion to indicate more fully in the course of 

 this review. 



In his third section he brings out his own views more 

 distinctly, corroborating the view of Weismann that every 

 structure is a useful adaptation which has been brought 

 about by natural selection acting in accidental infinitesimal 

 changes in germ-plasm. At first sight it would seem that he 

 advocates the action of some distinctive vital power, but this 

 he categorically denies. 



* I repudiate,' he declares,^ ' any special internal force of evolu- 

 tion. According to my view, everything in evolution is due to . . . 

 material, physical causes, . . . a " crystallisation," resulting from the 

 physical and chemical action of external agents on the material of the 

 organism subjected to them.' 



This idea we will consider presently ; for the present we 

 will limit our attention to his opposition to Weismann's 

 views as to the distinction between unicellular and multi- 

 cellular animals with respect to immortality. He would 

 place some limits to the immortality of the former on 

 account of their 'metabolism' — that is, the constant minute 

 changes in their structure which are inseparable from life. 

 As to multicellular organisms, he admits the mortality of the 

 general substance of their body — their soma — because 'the 

 latter is not really an end in itself.' But, as his translator, 

 Mr. Cunningham, very pertinently observes: 'It would be 



1 P. 6U 



