No. 575] RESPONSES OF PLANTS AND ANIMALS 665 



of a group of investigators among whom Weismann was 

 a conspicuous leader, problems of the germ cells, the 

 egg's early development, and heredity, became "funda- 

 mental problems." They evidently argued that since all 

 comes from the egg and germ cell, all must be discover- 

 able in the egg. If germ plasm were as independent from 

 soma, as completely insulated from environment as con- 

 tinuous from generation to generation as has been 

 assumed, the study of germ plasm would be the only way 

 to the solution of the problems of heredity and evolution. 

 This follows no matter whether the chromosomes or 

 almost the entire egg are credited with carrying heredi- 

 tary qualities; only the postulation of continuity and 

 independence from soma and insulation from environ- 

 ment are necessary. If the independence of germ plasm 

 from soma be accepted even in a weakened and modified 

 form it follows that studies of somatic characters can at 

 most be of secondary importance from the point of view 

 of heredity and evolution. Thus in some quarters the 

 value of various lines of zoological work has been esti- 

 mated largely, unconsciously, no doubt, in proportion to 

 the nearness or remoteness of their relation to the "germ 

 plasm" question. 



Thus it is true that in biology as in all other fields 

 values are measured consciously or unconsciously by 

 criteria. In recent years another better criterion of value 

 has made its appearance among zoologists. The germ 

 plasm criterion already discussed was primarily morpho- 

 logical; the second is physiological, borrowed no doubt 

 from physiologists. It measures values on the basis of 

 the analysis of the organisms into terms of physics and 

 chemistry or is concerned with a mechanistic conception 

 of life in all its manifestations. From this viewpoint the 

 study of each and every part of the organism is important 

 because the discovery of laws governing one part is 

 usually or at least often of general importance. Investi- 

 gations from this viewpoint have shown that the germ 

 plasm criterion is clearly illogical in its application to the 

 study of somatic characters because it is based upon the 



