STABILITY OF THE GENE 301 



influence of the body itself on the constitution of the gene 

 has been only touched upon. The clean separation of the 

 genes in the hybrid, that is the basal postulate of Men- 

 del's first law, would not be possible if genes were sub- 

 ject to influences from the bodily characters of the hybrid. 



This conclusion brings us face to face with the La- 

 marckian theory of the inheritance of acquired charac- 

 ters. It would take us too far afield to attempt to consider 

 the varied claims of this theory, but I may be allowed to 

 call attention to certain relations that would be expected, 

 if, as this theory postulates, the germ-cells are affected 

 by the body in the sense that a change in a character may 

 bring about corresponding alterations in specific genes. 

 A few examples will illustrate the essential facts. 



When a black rabbit is bred to a white rabbit the hy- 

 brid young are black, yet the germ-cells produced in this 

 hybrid are black- or white-producing, in equal numbers. 

 The black hair of the hybrid has no influence on the white 

 germ-cells. No matter how long the genes for white are 

 carried by black hybrids, the white genes remain white. 



Now if the white gene is interpreted as an entity of 

 some sort, it should show, if the Lamarckian theory 

 holds, some effect of the body character of the individual 

 in which the gene is carried. 



Suppose, however, the white gene is interpreted as the 

 absence of the black gene. Then, of course, there is no 

 reason for supposing that the black color of the hybrid 

 could produce any influence on nothing. To anyone hold- 

 ing the presence and absence theory this argument 

 against Lamarck's theory is not cogent. 



There is, however, another line of approach that may 

 be more to the point. A white four-o'clock, bred to a red 

 one, produces an intermediate hybrid with pink-colored 

 flowers (Fig. 5). If we interpret the white color as an 

 absence, the red must be due to a presence. The color of 



