Stimmary. 105 



further theory of evolution it is necessary to make 

 this further postulate of the stability of germ-plasm 

 as undisturbed since the first origin of sexual propaga- 

 tion : otherwise there would be no logical foundation 

 for any of the distinctive doctrines which go to 

 constitute that theory. 



Thus much understood, we proceeded to examine 

 the theory of germ-plasm in each of its departments 

 separately — i.e., first as a theory of heredity, and 

 next as a theory of evolution. And we begun by 

 comparing it as a theory of heredity with the pre- 

 ceding theories of Darwin and Galton. In the result 

 we found that germ-plasm resembles gemmules in all 

 the following respects. It is particulate; constitutes the 

 material basis of heredity; is mainly lodged in highly 

 specialized cells ; is nevertheless also distributed 

 throughout the general cellular tissues, where it is 

 concerned in all processes of regeneration, repair, and 

 a-sexual reproduction ; presents an enormously com- 

 plex structure, in that every constituent part of 

 a potentially future organism is represented in a fer- 

 tilized ovum by corresponding particles ; is every- 

 where capable of virtually unlimited multiplication, 

 without ever losing its hereditary endowments ; is 

 often capable of carrying these endowments in a dor- 

 mant state through a long series of generations, until 

 at last they re-appear again in what we recognize as 

 reversions. Such being the points of resemblance, the 

 only points of difference may be summed up in the 

 two words — continuity, and stability. For, as regards 

 continuity, while Darwin's theory supposes the sub- 

 stance of heredity to be more or less formed anew in 

 each generation by the body-tissues of that generation, 



