CHAPTER X 



THE GERM-PLASM THEORY 



In discussing the germ-plasm theory it is necessary 

 to distinguish between this hypothesis and that of 

 the morphological continuity of the germ cells. The 

 facts and theories involved have grown up to- 

 gether. Owen (1849) was perhaps the first to 

 point out the differences between germ cells and body 

 cells. "Not all of the progeny of the primary impreg- 

 nated germ cell," he writes, "are required for the for- 

 mation of the body in all animals ; certain of the de- 

 rivative germ cells may remain unchanged and become 

 included in that body which has been composed of 

 their metamorphosed and diversely combined and 

 confluent brethren; so included, any derivative 

 germ cell or the nucleus of such may commence and 

 repeat the same processes of growth by imbibition, 

 and of propagation by spontaneous fission, as those 

 to which itself owed its origin. ..." Galton (1872) 

 was among the earliest to recognize the necessity 

 for two sorts of materials in the individual metazoon, 

 "one of which is latent and only known to us by its 

 effects on his posterity, while the other is potent, 

 and constitutes the person manifest to our senses." 

 He at that time believed in the inheritance of ac- 

 quired characters and conceived the egg as a struc- 



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