50 BIOLOGICAL SOCIETY OF WASHINGTON. 



that other variations are taking place due to unknown causes 

 and that these are seized upon by natural selection to the 

 advantage of the species. 



The difficulty, on Weismann's theory, of accounting for any 

 variation at all above the protozoans still confronts us. If ex 

 ternal influences can only act on unicellular organisms in such 

 a way as to be transmitted, it must follow that so soon as the 

 multicellular stage is reached a rigid fixity must result. One 

 of these lower metazoans may undergo important modifications 

 during its lifetime, but its offspring are always set back to pre 

 cisely the same place where the parent was when it set out. 

 All these functionally produced changes are, according to him, 

 utterly lost because they cannot react upon the germ-plasm. 

 Where is the room for the action of natural selection ? He has 

 not dwelt upon this point, but he would probably say, though 

 contrary to statements above quoted, that the germ-plasms are 

 constantly undergoing spontaneous variation and that natural 

 selection works on these. We would then be brought back to 

 where we were a moment ago, with the question still before 

 us, how spontaneous variations differ from functional ones (for 

 he would not maintain that they were wholly uncaused effects), 

 and why it is not logical and rational to assume that functional 

 changes are impressed upon the germ-cells in ways which, 

 though unknown to us, are no more unknown than is the cause 

 of spontaneous variations. This seems to be far more reason 

 able than the far-fetched, and, as it seems to me, childish view 

 recently expressed by Prof. E. Ray Lankester, that the envi 

 ronment does indeed influence the germ-cells but only by 

 kaleidoscopically shaking up their contents, thus causing what 

 are called ' ' sports ' ' in the progeny, and that natural selection 

 seizes upon these, thereby securing advantageous transfor 

 mations. 



