OOGENESIS IN THE WHITE MOUSE 279 



'36 to 40). The chromatin loses more and more its staining 

 reaction and the nucleus appears filled with more or less isolated 

 strands and granules of faintly staining chromatin. These 

 strands are eventually arranged as smaller masses and threads 

 of irregular form, with granules scattered here and there, and 

 with a faint, irregular, incomplete reticulum of linin. Two or 

 three nucleoli are usually visible, one frequently larger and less 

 intensely stained than the others (figs. 41 to 46). 



This condition of the nucleus, with the chromatin widely 

 scattered in irregular granules and strands and with two or three 

 nucleoli, resembles to a certain extent the 'dictyate' stage de- 



Text fig. 7 A definitive oocyte in a mature or nearly mature Graafian follicle. 

 This is a sketch of the oocyte whose nucleus is shown in figure 46. The follicles of 

 the mouse do not attain the large size nor the marked vesicular character of those 

 of many other mammals. X 44. 



scribed above for the primitive germ cells. This is not surprising, 

 perhaps, when it is considered that the 'dictyate' stage of the 

 primitive germ cell and stage 'c' of the definitive oocyte are each 

 correlated with the enormous growth of the germ cell and its 

 nucleus. Compare, for example, figure 36 with 46; the latter 

 oocyte is so large that only the nucleus is shown in the drawing. 

 This oocyte (fig. 46) is in a nearly mature Graafian follicle 

 (text fig. 7) and is almost ready for maturation. 



As the oocytes enter stage 'b,' they begin to grow in size and, 

 although at first more or less rounded, they become more oval, 

 with their long axes tangential to the surface of the ovary; but 

 their shape is apparently dependant on pressure and the effect 

 of the adjacent cells. Oocytes in stages 'a' and 'b' are found 

 in the germinal epithelium, and occasionally cells of stage 'c' 



