n6 THE PHYSIOLOGY OF REPRODUCTION 



which chiefly concern the chromatin of the nucleus may be 

 summarised as follows : 



I. Early changes : () Protobroque cells, Variety a. The nuclei 

 are granular in appearance, the chromatin is arranged irregularly, 

 and there is no reticulum. These are the original germinal epithelial 

 nuclei. (b) Protobroque cells, Variety b. The cells belonging to 



Early ovogenetic stage. 



Leptotenic stage. 



FIG. 29. Developing ova from ovary two days before birth. (After 

 Lane-Claypon.) 



variety a divide, and give rise to more cells of the same kind, as 

 well as to protobroque cells of the b variety. In the latter the 

 nuclei are less granular, and contain a certain number of fine 

 chromatin filaments, (c) Deutobroque cells. The protobroque cells 



Early. Synaptenic stage. Late. 



FIG. 30. Developing ova from ovary about one day before birth. 

 (After Lane-Claypon.) 



of the b variety likewise divide, and give rise to more protobroque 

 cells, similar to themselves and also to deutobroque cells. These 

 latter are larger in size, and contain nuclei with the chromatin 

 arranged in the form of a reticulum. 



II. Later changes: (a) Leptotenic stage. Certain of the 

 deutobroque nuclei become gradually differentiated, the chromatin 

 during the leptotenic stage passing through a process in which it 

 breaks up into fine filaments ; these are distributed over the nuclear 

 region, (b) Synaptenic stage. The filaments become congregated 



