254 



Action of the Genetic Material 



present previously in the stalk and, therefore, should contribute to 

 the result until exhausted. Afterward, a purely nuclear effect should 

 prevail. This could be determined by producing uninuclear combina- 

 tions of stalks from different species. Indeed, early umbrellas were 

 intermediate; later ones followed the species which supplied the 

 nucleus. In these experiments it turned out also that the stuffs which 

 control the specific features of the umbrella are different from those 

 which are responsible for the formation of any umbrella at all. 



Fig. 16. Right, A. Wettsteini; left, mediterranea; center, transplantation of 

 mediterranea stem on Wettsteini base and formation of Wettsteini cap on re- 

 generate. Lines of cuts indicated. (From Hammerling, 1953.) 



At this point one might be inclined to bring in cytoplasmic 

 heredity, because the nucleated section always contains some cyto- 

 plasm. (Experiments with nuclear transplantation have not been 

 made.) Such cytoplasm may act independently and be self -propagat- 

 ing. The following fact is not in favor of such an assumption (Ham- 

 merling, 1953). In the species acicularia no regeneration of a cap 

 occurs in the absence of the nucleus, and in its presence only 15 per 



