THE PRESENT POSITION OF CELL-THEORY. 231 



has given a true account of the minute structure of proto- 

 plasm, so far as it can at present be determined by optical 

 means. And I even venture to prophecy that when the 

 history of the biological work of this half century comes to 

 be written some half century hence, the theories of biophors 

 and plasomes and the such like will have merely a historical 

 interest, whilst the work of Biitschli will be regarded as the 

 most sagacious and far-sighted contribution of our time to 

 this momentous question. In saying this I do not wish 

 to declare my adhesion to the more theoretical part of 

 Biitschlis work, but only to his account of the microscopic 

 structure of protoplasm. 



Even if one were to accept his explanation of the 

 streaming movements there would remain all the other 

 phenomena of life to be accounted for, and they are inex- 

 plicable on the visible structure of protoplasm, even if it be 

 an alveolar structure. 



Underlying the visible structure then there must be an 

 invisible structure, which is the cause of the phenomena. 

 This admission once made, the claims of the rival theories 

 of biophors, plasomes, plastidules and what not, again press 

 themselves on our attention. Now it is to be remarked 

 that the most cautious and thoughtful theorists do not claim 

 that their hypothetical units are an explanation of life. 

 Weismann categorically denies that his theory of the germ 

 plasm is a theory of life, it is only a theory of heredity, but 

 he goes so far as to suggest that a workable explanation of 

 the more complicated vital phenomena may be the surest 

 indication of the path which will lead to an explanation of 

 the more simple (loc. ciL, p. 21). 



Others, however, are not so cautious, and in any case 

 there is this feature common to all, that they aver on the 

 one hand that vital processes are so complicated that they 

 cannot be explained by a physico-chemical theory of the 

 constitution of protoplasm, and that therefore we must 

 assume the existence of ultimate vital units or biophors : 

 on the other hand, after endowing these biophors with all 

 the attributes of life, they say that they have a comparatively 

 simple molecular constitution upon which the phenomena 



