Characters as Adaptive and Specific. 243 



signify in such a case whether the changed con- 

 ditions of life first affected the soma, and then, through 

 changed nutrition, the germ-plasm ; or whether 

 from the first it directly affected the germ-plasm itself. 

 For in either case the result would be a " species," 

 which would continue to reproduce its peculiar 

 features by heredity. 



Now, the supposition that changed conditions of life 

 may thus affect the congenital endowments of germ- 

 plasm is not a gratuitous one. The sundry facts 

 already given in previous chapters are enough to 

 show that the origin of a blastogenetic species by the 

 direct action on germ-plasm of changed conditions 

 of life is, at all events, a possibility. And a little 

 further thought is enough to show that this possibility 

 becomes a probability — if not a virtual certainty. 

 Even Weismann — notwithstanding his desire to main- 

 tain, as far as he possibly can, the "stability" of 

 germ-plasm — is obliged to allow that external con- 

 ditions acting on the organism may in some cases 

 modify the hereditary qualities of its germ-plasm, and 

 so, as he says, " determine the phyletic development 

 of its descendants." Again, we have seen that he is 

 compelled to interpret the results of his own experi- 

 ments on the climatic varieties of certain butterflies 

 by saying, " I cannot explain the facts otherwise than 

 by supposing the passive acquisition of characters 

 produced by direct influences of climate " ; by which 

 he means that in this case the influence of climate 

 acts directly on the hereditary qualities of germ- 

 plasm. Lastly, and more generally, he says : — 



" But although I hold it improbable that individual variability 

 can depend on a direct action of external influences upon the 

 R a 



