< SIMPLE PROTOPLASM ' 53 



mechanistic theory, put aside from our minds 

 all the hazy ideas of former generations as to 

 the structure of living cells being nothing but 

 that of an indefinite ' plasma.' Such ideas 

 belong to the early childhood of physiology. 

 We now know that 'simple protoplasm' 

 exists nowhere, not even among the most 

 primitive protozoa or bacteria. Modern in 

 vestigation of the complex and intensely 

 specific functional activities of every variety 

 of living organism or cell has relegated the 

 old ideas, derived from mere microscopic 

 examination, to oblivion. What the mech 

 anistic theory must assume in the case of an 

 organism such as man is a vast assemblage 

 of the most intricate and delicately adjusted 

 cell-mechanisms, each mechanism being so 

 constituted as to keep itself in working order 

 year after year, and in exact co-ordination 

 with the working of the millions of other 

 cell-mechanisms which make up the whole 

 organism. 



This assumption is surely one which taxes 

 scientific imagination to the utmost, but let 

 us make it and continue the argument. We 

 have now to imagine the mechanism of repro- 



