ACCOUNT OF THE GERM-CELL CYCLE 41 



until, as shown in Fig. 7, the central part of the 

 oocyte consists of homogeneous cytoplasm (cy) 9 and 

 the outer region of the cytoplasm is crowded with 

 granules and spherical bodies of various sizes. 

 Apparently the mitochondria lying near the periphery 

 (Fig. 8, H) increase in size, gradually losing their 

 affinity for the crystal violet stain and swelling up 

 until they constitute the large yolk globules so 

 numerous in the mature egg. All stages in the 

 evolution of these bodies are illustrated at this time 

 as represented in Fig. 8, H. In the meantime 

 material is brought into the egg through the egg 

 string from the nurse cells, thus probably adding 

 several sorts of granules to the contents of the oocyte. 



The growth period in the male germ-cell cycle is 

 not so striking as in the female, since many sperma- 

 tozoa of small size are produced, whereas only 

 comparatively few large eggs develop. An increase 

 in the size of the ultimate spermatogonia may occur, 

 however, but the multiplication and growth periods 

 are not nearly so distinct as in the case of the oogonia. 

 In testes which are composed of cysts of spermato- 

 gonia there is evidence in some cases that all of the 

 germ cells in a single cyst are descendants of a single 

 spermatogonium. The proof for this seems certain 

 in the potato beetle, where I have been able to 

 follow the formation of the cysts by means of an 

 uninterrupted series of stages (Hegner, 1914a). 



7. MATURATION. Maturation or the ripening 

 of the eggs and spermatozoa comprises a series of 

 events which results in a reduction in the number 



