134 ORGANIC EVOLUTION — THE FACTOES 



the rest of it. So far from it being true that in the 

 lower animal world acquired traits are not transmis- 

 sible, it is precisely there, in the lowest, that they are 

 distinctly transmissible. In that stratum of life which, 

 in our imperfect knowledge, we at present regard as 

 the lowest, where the plant and animal kingdoms 

 merge, and whence both have arisen, every organism 

 .being unicellular is a germ cell, which, besides being 

 extremely minute and relatively simple, is one on which 

 external conditions act directly, whereby the constitu- 

 tion of the cell is so modified that a like variation is 

 produced in the next generation. For this reason, as 

 already indicated, bacteriologists, by means of their 

 "attenuated cultures," are able to deeply modify the 

 characteristics of microbic organisms. As regards higher 

 animals, the high multicellular animals with which 

 alone Mr. Spencer deals in his paper, nothing that he 

 has said, and nothing that any one else has said, 

 establishes a shadow of proof that in them acquired 

 traits are transmissible — that the changes, which the 

 action of the environment produces in their somatic cells, 

 so affect their germ cells, that these latter, when they 

 proliferate, reproduce in the new organism variations 

 like to those which the action of the environment pro- 

 duced in the parent. 



