102 SCIENCE PROGRESS. 



The point for present consideration is this : Is it neces- 

 sary for the explanation of vital phenomena to assume 

 the existence of ultimate vital particles, so minute as 

 to be invisible with the best microscopical powers 

 which we possess, each of which is to be considered 

 as being in posse an independent organism capable of 

 displaying some of the most characteristic of vital pheno- 

 mena, viz., assimilation, growth, metabolism, reproduction 

 by division ? 



As it will be necessary to refer frequently to these 

 assumed vital units, I must call them by some name, and I 

 shall use Weismann's term biophor, without meaning to 

 exclude the conceptions of other authors, the pangenes of 

 De Vries, the plasomes of Wiesner and so forth. I use the 

 term biophor in the sense of Lebenstrager, the bearer of the 

 vital properties, without necessarily implying that it pos- 

 sesses all the particular properties assigned by Weismann 

 to his biophors. 



Whatever the point from which the different authors 

 have started, they all postulate the existence of minute 

 biophors on the grounds that the vital phenomena exhibited 

 by cells, say by an Amoeba, or by the ovum of a Metazoon, 

 imply the existence of an organisation adequate to the 

 production of the observed processes. The life processes 

 are too various and too complicated in their kind to be 

 explained by the visible constitution of protoplasm, even if 

 it be allowed, as it generally is allowed, that protoplasm is 

 not a chemical compound of fixed molecular composition 

 but a mixture of many chemical substances, each having a 

 molecular composition of some considerable complexity. I 

 have already shown that Schwann himself was possessed of 

 such an idea, which he expressed sufficiently clearly when 

 he referred to " a peculiar mode of union of the atoms 

 to form atoms of the second order," but he did not attempt 

 to follow out the idea, confining himself to the inquiry 

 into " the arrangement of these conglomerate molecules 

 when forming either the separate elementary parts of 

 organisms or the entire organism ". The term consdomer- 

 ate molecule is in fact synonymous with the term biophor 



