24 BIOLOGICAL LECTURES. 



consistently gave to his provisional hypothesis the name of 

 pa7igenesis, since the minute latent buds of the germ were 

 supposed to come from, and thus represent potentially, every 

 part of the bodies of the parents, and possibly of still remoter 

 ancestry. 



With the discovery of the presence of germinal substance in 

 multicellular organisms, from the embryonic stages onwards, 

 by Owen, Galton, Jager, Nussbaum, and others, the theory of 

 continuity of germinal matter came into vogue. Upon this 

 basis Weismann distinguished two kinds of plasma in multicel- 

 lular beings ; namely, the germ-plasm and the body-plasm, and 

 at first assumed that because of this separation the latter 

 could not modify the former, since the fate of the respective 

 sorts of plasma was predetermined by virtue of this separation. 

 The one kind was the mere carrier of the other, and the germ- 

 plasm was immortal because it was produced in each species 

 from a store of it which always existed, either in a latent or 

 palpable form, from the very beginning of development. He 

 seems, however, in recent years, to have admitted that this 

 germ-plasma could be indirectly modified in constitution 

 through the influence of the body-plasm, that bore and en- 

 closed it. Beyond this point Weismann again becomes a 

 preformationist, as truly as Democritus, in that he now con- 

 jectures that the supposed innumerable latent buds of the 

 germ, representative of the organs of the future being, are 

 minute masses which he sees as objective realities in the 

 chromosomes of the nuclei of the sex-cells. These chromo- 

 somes of the germ he calls "ids" and "idants," according to 

 their condition of sub-division, and supposes them to grow 

 and become divided into "determinants" and "biophors," in 

 the course of embryonic development. To these he ascribes 

 powers little short of miraculous, in that he asserts that these 

 infinitesimal germinal particles grow and divide just at the 

 right time and order, and control development so as to build 

 up anew the arrangement of parts seen in the parent type. 

 This elaborate system of preformationism is bound to produce 

 a reaction, that is already becoming apparent ; in fact, it is 

 probable that its very complexity, its many inconsistencies, as 



