THE DUALITY OF INHERITANCE 



material, so far as heredity is concerned, is 

 evidently found in egg and sperm alike. It 

 is plainly small in amount and possibly con- 

 sists merely in ferment-like bodies which, ini- 



FIG. 1. Egg and sperm (s) of the sea-urchin, Toxopneustes, 

 both shown at the same enlargement. (After Wilson.) 



tiate certain metabolic processes in a suitable 

 medium represented by the bulk of the egg. 

 The amount of a ferment used in starting a 

 chemical change bears no relation, as is well 

 known, to the amount of the chemical change 

 which it can bring about in a suitable medium. 



9 



