Acquired Modifications Heritable ? 109 



which affect only the body of the chicken can 

 influence later chickens, because the only 

 direct connection between the chick and its 

 offspring is back through an egg which goes 

 out of existence as it develops into the chick 

 and more of the germ plasm. 



In several animals we have evidence of this 

 early separation of the soma plasm from the 

 germ plasm. Even in the four-cell stage of the 

 developing egg of Ascaris, a round worm com- 

 mon in the intestine of the horse and hog, the 

 body cells are marked off from the germ cells 

 by the fact that certain portions of the chromo- 

 somes disappear in the body cells, while they 

 remain in the germ cell. Thus only one cell of 

 the four continues as germ material, while the 

 other three give rise to the body cells. Simi- 

 larly, in Miaster, one of the flies, the somatic 

 cells are clearly distinguished from the germ 

 cells by the eight-cell stage of the developing 

 egg. And in many other animals we can trace 

 this separation back to an early stage in develop- 

 ment. We seem to have, then, fairly positive 

 evidence that Weismann's contention is correct, 



