Weismann s theory of Heredity (1891). 83 



that is required in order to produce a seminal hybrid 

 by means of sexual cells. On the contrary, in the 

 former case most, if not all, the somatic-cells which 

 are brought into apposition by the graft must be 

 supposed thus to mix their nuclear contents at the 

 plane of the graft ; for otherwise the hybrid would not 

 afterwards present equally the characters of stock and 

 scion. Now, there may be hundreds of thousands of 

 such cells, and therefore it seems impossible that the 

 facts of graft-hybridization can be reconciled with the 

 theory of germ-plasms 1 . 



The third line of evidence against this theory — 

 i.e., the evidence in favour of the transmission of 

 acquired characters — is to constitute the subject- 

 matter of future chapters. Therefore it will here be 

 sufficient to adduce only one fact of this kind. And 

 I select it because it is one that has been dealt with by 

 Weismann himself. In one of his more recent state- 

 ments he says : — 



The distinguished botanist De Vries has proved that certain 

 constituents of the cell body — e. g., the chromatophores of 

 Algae — pass directly from the maternal ovum to the daughter 

 organism, while the male germ-cells generally contain no 

 chromatophores. Here it appears possible that a transmission 

 of somatogenetic variation has occurred 2 . 



Now although, as Weismann goes on to observe, 



1 Possibly the school of Weismann may simply refuse to accept the 

 facts, which are confessedly rare, and, in many of the cases alleged, 

 dubious. In other cases, however, the evidence is sufficient to have 

 satisfied the cautious judgement of Darwin, who has discussed it in 

 detail. Therefore, even if the Neo-Darwinians repudiate this evidence, 

 at least they ought to state that such is the position which they 

 adopt. 



2 Nature, Feb. 6th, 1890. 



G 2 



