GENETICS 87 



is largely responsible for the development attained 

 by the cytoplasm; (2) that the cytoplasm is pri- 

 marily a plastic material of construction which 

 must, like the chromatin, be handed down from 

 a previous generation; (3) that inheritance through 

 the cytoplasm is primarily inheritance of ma- 

 terials, while inheritance through the chromo- 

 somes, which must also involve special materials, 

 is primarily inheritance of potentialities for shaping 

 these materials and for their elaboration and di- 

 versification; and (4) that these facts are harmoni- 

 ous with the constant association of heritage with 

 environment, both external and internal, in the 

 production of living things. It is doubtful whether, 

 under these conditions, the statement that the 

 cytoplasm may be "ignored genetically" is justi- 

 fied. It seems rather to be a factor which is nor- 

 mally constant in the various cells of a given 

 species. 



The relations of nucleus, or chromosomes, and 

 cytoplasm are somewhat similar to the relations of 

 germ plasm and soma, to which Weismann's work 

 gave a prominent place in biology. Indeed, the 

 germ plasm has been called identical with chromo- 

 somes and the soma with cytoplasm. In sexual 

 organisms the individual usually springs from a 

 fertilized ovum which is regarded as germ plasm, 

 as also are those cells which lead from it to the 

 germ cells developed in the new body, while all 



