Summary. 1 1 1 



or vice vei'sa, which proves the possibility of a trans- 

 mission of hereditary characters by a mere grafting 

 together of somatic tissues ; the direct evidence given 

 by De Vries that in certain Algae constituents of 

 cellular tissue pass immediately from the maternal 

 ovum to the daughter organism ; and the evidence, 

 both direct and indirect, which remains to be given 

 on a larger scale in my subsequent volume, where we 

 shall have to challenge the validity of Weismann's 

 fundamental postulate touching the non - occurrence 

 of Lamarckian factors in any of the multicellular 

 organisms. 



It must here again be noticed that in those passages 

 where he concedes the possibly e; occasional " trans- 

 mission of acquired characters Weismann is anni- 

 hilating his own theory, root and branch. Thus, for 

 example, in allusion to De Vries' observation just 

 mentioned, he says that we cannot exclude the 

 possibility of " changes being induced by external 

 conditions in the organism as a whole, and then com- 

 municated to the germ-cells after the manner in- 

 dicated in Darwin's hypothesis of pangenesis." But 

 it is obvious that the theory of germ-plasm must 

 "exclude the possibility of such a transmission occa- 

 sionally occurring ; ' ; for the very essence of that 

 theory consists in its postulating a difference between 

 germ-plasm and the general body-substance in kind, 

 such that there never can be any " communication " 

 from the one to the other " after the manner indicated 

 by Darwin's hypothesis of pangenesis." Any pre- 

 varication over this point amounts simply to aban- 

 doning the theory of germ-plasm altogether, and 

 opening up a totally distinct issue — namely, the 



