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 metazoén, 
“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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