LIFE AND DEATH. 291 



Wien, 1899, B. I. and II., where the collected literature may 

 be found, and the reader introduced to the huge mass of 

 controversial writings put forward since Darwin and asso- 

 -ciated with the names of Weismann and others. 



It will probably be noticed that I have employed the term 

 molecular unit of protoplasm, and have not discussed the 

 question of organised structure in the latter : this is because 

 it seems clear to me that living protoplasm as such does 

 not possess "organised structure" in the true sense of that 

 term it is, rather, busy preparing and making "organised 

 structure," and a molecular constitution would have to be 

 ascribed to all " physiological units "' of the nature of 

 micellae, pangens, ids, etc., as truly as to the structural units 

 of a starch-grain or cell-wall, or even of a crystal. In this 

 connection, the student will find the necessary points of 

 view put forward in Pfefifer, Physiology^ pp. 37-83. 



