GERMINAL SELECTION. 41 



molecules, for molecules are neither nourished, sub- 

 ject to growth, nor propagated. 



The gradual degeneration of organs grown useless 

 may be explained, now, by the theory of determinants 

 very simply and without any co-operation on the part 

 of active personal selection, as follows. 



Nutrition, it is known, is not merely a pas- 

 sive process. A part is not only nourished but 

 also actively nourishes itself, and the more vigor- 

 ously, the more powerful and capable of assimila- 

 tion it is. Hence powerful determinants in the germ 

 will absorb nutriment more rapidly than weaker deter- 

 minants. The latter, accordingly, will grow more 

 slowly and will produce weaker descendants than the 

 former. 



Let us assume, now, that a part of the body, say 

 the hinder extremities of the quadruped ancestors of 



units," to use Wiesner's phrase. Of course this particular 

 aspect of the vital units was not emphasised by Brucke with 

 the same distinctness and sharpness as by recent inquirers, 

 who took up Briicke's ideas thirty years after. I refer to ^ 

 the conception that the union of a definite combination qf 

 heterogeneous molecules into an invisibly small unit, forms 

 the cradle of focus of the vital phenomena. This was first 

 done and apparently on independent considerations by De 

 Vries, and soon after by Wiesner, and subsequently by myself , 

 (De Vries, Intracelluldre Pangenesis, Jena, 1889; Wiesner, 

 Die Elementarstructur und das Wachsthum der lebenden 

 Substans, Vienna, 1892; Weismann, Das Keimplasma, Jena, 

 1892). Let me say at the close of this note that it is not my 

 intention in thus defending the rights of a great physiologist, 

 to censure in the least the distinguished author of L'heredite 

 who has set himself a remarkably high standard of exactitude 

 in such matters. Certainly, when we consider the enormous 

 extent of the literature that had to be mastered to produce 

 his bo&k, embracing as it did all the various theories of recent 

 times, such an oversight is quite excusable. 



