Elsberg's Plastidules 45 



descent, and are, therefore, materially based on the dif- 

 ferences of the plastidules. Systematic affinity depends 

 upon the possession of the same plastidules, systematic 

 differences on the presence of different molecules in addi- 

 tion to the bulk of those that are alike. 



Haeckel, who, in his "Generelle Morphologic," had 

 not yet considered the significance of the molecule for the 

 theory of heredity, 12 has further carried out Elsberg's 

 train of thought 13 in his above mentioned monograph. 

 "The sum total of physical and chemical processes, called 

 life, is evidently conditioned in the last instance by the 

 molecular structure of the plasson." 1 * In the non-nu- 

 cleated plasson (or protoplast) the plastidules are every- 

 where uniform; in the. nucleated ones they are differen- 

 tiated in such a manner that a distinction must be made 

 between plasmodules and coccodules (nucleo-molecules). 

 The differentiation of the organism into organs, and the 

 division of labor thereby achieved, Haeckel attributes to 

 a division of labor of the plastidules, for in this way they 

 are segregated more or less, and thus produce the various 

 kinds of protoplasm. Fertilization consists in the fusion 

 of two protoplasts which have developed in different 

 directions through a far-reaching differentiation of their 

 plastidules. 15 



We will limit ourselves to this part of the theory of 



12 Only in a general way does Haeckel point here to the signifi- 

 cance of "the numerous and minute differences in the atomic con- 

 stitution of the protein-compounds, which form the plasma of the 

 plastids." Gen. Morphol 1: 277. 



13 Elsberg later (Proc. Amer. Assoc. Adv. Sci. 25: 178. 1877.) in- 

 sisted that he had been misunderstood and misinterpreted by Haeckel 

 in the monograph above referred to. Tr. 



l4 Perigenesis. p. 34. 



15 Loc. cit. p. 52. 



