EVOLUTION AND HEREDITY. 1 33 



"evolution of the germ," or the expansion of a minute 

 pre-formecl individual, as opposed to Harvey's ''epigene- 

 sis,"or growth by addition, had given way to a modifica- 

 tion of both ideas: ''That development, which, in its 

 superficial aspect, is epigenesis, appears in essence to be 

 evolution or the expansion of a potential organism ac- 

 cording to fixed laws." ^ Darwin's views were thus 

 stated : ^ 



" It is universally admitted that the cells of the body increase by 

 self division thus forming the various tissues. Besides this, I assume 

 that the cell units throw off minute granules which are dispersed 

 through the entire system ; these may be called ge^nmules. They 

 are collected from all parts of the system to form the sexual elements, 

 and their development in the next generation forms the new being. 

 They are thrown off by every unit, not only during the adult stage 

 but during each stage of development of every organism. Hence it 

 is not the reproductive organs or buds which generate new organ- 

 isms but the units of which each individual is composed. Gemmules 

 are capable of transmission in a dormant state to future generations 

 and may then be developed." 



Notice two main features of this hypothesis : that 

 there is no difference of character in the elements con- 

 veyed by the two sexes ; second, that the vehicles of 

 hereditary characteristics are broken down, scattered 

 through the system, and ;r-collected from the soma or 

 body of each individual to form the germ of the new 

 one. There are, therefore, postulated countless numbers 

 of gemmules corresponding to the constantly changing 

 cells of the body ; these gemmules being also imaginary 

 elements. Their migration to and from the body cells 

 is in contrast with the fixity of the repetition of parental 



^ Huxley, Art. Evolution, Enc. Brit., p. 746. 



2 Variation of Animals and Plants under Domestication, vol. ii., p. 369. 



