88 GENETICS 



cell can overleap the barrier of cell division and appear 

 at the other end after mitosis. 



In his cultures Jennings found a Paramecium with 

 an abnormal spine at one end. This acquisition was 

 handed on for five generations before it disappeared 

 but never in any generation did more than one of the 

 offspring have the spine. In other words, it did not 

 become hereditary although it continually reappeared 

 in one individual in every generation. The reason for 

 this will be apparent upon referring to Figure 13. The 

 fission-half bearing the spine holds the same relation 

 to the spineless half as soma to germ and there is here 

 no mechanism for the transmission from one half to 

 the other. Simple transmission, like the persistence of 

 the spine for five generations of Paramecium is not 

 heredity. In order that a character shall be really 

 inherited, that is, shall appear in more than one of the 

 progeny and so affect the race, it must be produced 

 anew in each generation from a germinal determiner. 

 This is just as true for the protozoa as it is for the 

 higher organisms. 



13. THE OPPOSITION TO WEISMANN 



The opponents of Weismann point out, as a weak 

 place in his argument, the assumption that the germ- 

 plasm is so insulated from the somatoplasm as not to 

 be influenced by it. Weismann assumes, of course, 

 that the germplasm is isolated from the somatoplasm 

 very early in the development of the fertilized egg into 

 an individual, and that when once isolated it thereafter 



