THE GER:\I PLASM TIIKOKY 801 



of the nature and reactions of I lie clieinical constitu- 

 ents of protoplasm, for, as AVilsou flDbJ, p. (Ui) says, 

 *'The essential conclusion tluit is iudicatcd l)\ cvto- 

 logical study of the uuclear substance is, thai it is an 

 aggregate of many different chemical couipouents 

 which do not constitute a mere mechanical mixture, 

 but a complex organic system, and which inuhTgo 

 perfectly ordered processes of segregation and dis- 

 tribution in the cvcle of cell life." 



Some of the strongest evidence that the germ- 

 plasm must include cytoplasmic constituents is 

 afforded by the observations and experiments ch^aling 

 with the differentiation of the germ cells, especially 

 during early embryonic development. ^Fhe writer's 

 morphological and experimental studies of chrysom- 

 elid beetles seem to prove that the nuclei during 

 the cleavage stages are all potentially alike and that 

 it is the cytoplasm which decides their fate. Boveri's 

 experiments on the eggs of Ascaris likewise show 

 that the cytoplasm determines the initiation of the 

 chromatin-diminution process and controls the differ- 

 entiation of the germ cells. Furthernu)re, nuich of 

 the data in the preceding cha])ters indicates that the 

 non-nuclear substance which will beconu' segregated 

 within the primordial germ cell is present in a nu)re 

 or less definite region in the nndivided egg, being 

 gradually localized and separated from the other v\i^;^ 

 substances as cleavage progresses. 'V\\v })osili()n of 

 this germ-cell substance can in many ca.ses be (U'ter- 

 mined because of the presence ol niclusions ot vari- 

 ous sorts, but whether these keimbahn-determinants 



