SOMATOGENESIS 257 



chromatic complex is handed down from cell-generation 

 to cell-generation in the development of the soma re- 

 gardless of the type of tissue to be formed. The ques- 

 tion now logically follows : How can identical germinal 

 substance give rise to different products in different 

 cells? How can a nerve cell, for example, so depart 

 from its embryonic spherical form that its cytoplasm 

 becomes drawn out into enormously attenuated neu- 

 rones tingling with neuro-fibrils, while a cartilage cell, 

 with the same outfit of germinal determiners in its 

 nucleus, commits cytological suicide by the excessive 

 secretion of its cell wall ? 



DeVries in his theory of "intra-cellular pangenesis" 

 (1889) proposes, as a way out of this dilemma, enzy- 

 matic "pangenes," of which each nucleus contains a 

 complete set, that escape into the cytoplasm and so 

 control its differentiation, an explanation "which 

 nearly meets the present requirements and fits pres- 

 ent knowledge." It is the cytoplasm and not the 

 nucleus that differentiates, although the directing 

 stimulus for differentiation comes from the nucleus. 



This conception is diagrammatically shown in Fig- 

 ure 80, which figure, furthermore, explains how the 

 stamp of the germplasm upon the somatoplasm can 

 influence not only immediate cell-division but all subse- 

 quent ontogenetic divisions until the adult structure 

 results. 



6. "CYTOPLASMIC INHERITANCE" 



While the germinal determiners in the chromosomes 

 are being apportioned to the daughter cells in mito- 

 sis with strict impartiality, the cytoplasm surrounding 



