130 



THE SCIENCE OF BIOLOGY 



to be quantitatively and qualitatively equivalent. Fig. 

 12 A, B, and C is diagrammatic in this particular. 



It thus appears that the oosperm, from which the adult 

 organism arises by cell division (Fig. 12), is composed of 



FIG. 15. Male and Female Pronuclei in Oosperm 

 and Early Cleavage. A, oosperm at be- 

 ginning of first cleavage showing the male 

 and female pronuclei; B, metaphase of 

 same; C, telophase; D, the two cell stage 

 with one cell still showing a double nucleus. 

 (Redrawn from figures by Agar after 

 Amma.) 



equal amounts of chromatin derived from the two parents, 

 but of a very disproportionate amount of cytoplasm. If the 

 latter were important as the vehicle by which the potential- 

 ities of the adult are carried over, we should expect an animal 

 to inherit a disproportionate number of its adult features 

 from the female parent. This is not the case. In general, 

 the inherited features appearing in the adult are equally bal- 

 anced. We therefore suspect that the chromatin which is 

 the material within the germ-cells that comes in equal 

 quantities from the two sexes is the basis of heredity. 

 A further word of explanation may be given regarding the 



