272 H. M. KINGERY 



ad\'isablo to take up the development of the first or 'primitive 

 germ cells' because of the part they play in the morphogenesis 

 of the ovary, and because von Winiwarter and Sainaaont have 

 described the history of these cells in the cat mth so much 

 attention to detail, as 'oogenesis.' 



It was stated abo\'e that this first proliferation of cells from 

 the germinal epithelium is a continuous process, but it should 

 be understood that the rate of proliferation is not uniform. It 

 is well marked in embryos from 12 to 22 mm. length (ca. fifteen 

 to nineteen days post coitum), when it becomes slower. From 

 this time on it is rather slow and at about three days post partum 

 it has ceased altogether and the second proliferation has begun. 

 This second state of activit}^ on the part of the germinal epithe- 

 limn is manifested rather slowly, and it is over shortly before 

 sexual maturity. It may be that the two proliferations in the 

 mouse are parts of one process, the second (post partum) being 

 a continuation of the first ; the discussion of this will be taken up 

 later. 



The earlier stages of the nuclear development of these germ 

 cells of the first or embryonic proliferation, the 'primitive oocytes,' 

 are usually passed through by the cells while still in the germinal 

 epithelium. After a number of cell-divisions a cell begins to 

 differentiate. The resting stage after each mitosis von Wini- 

 warter calls 'protobroque.' After the last oogonial mitosis in 

 the mouse, the cell returns to this stage (fig. 14). The nucleus 

 shows a delicate network of chromatin on a reticulum of linin. 

 At the intersections the chromatin is massed in larger granules, 

 among which are two or three nucleoli, one of which is usually 

 larger than the others. With Flemming's fluid and triple stain, 

 the red nucleoli stand out distinctly from the blue- violet reticulum 

 of chromatin. No idiosome is seen at this stage, and the mito- 

 chondrial content is made up of granules sparsely scattered 

 through the cytoplasm. Cells in this phase are found in the 

 germinal epithelium, in embryos from 13 mm. length up to birth. 



There is no indication of the stages 'poussieroide' or 'deuto- 

 broque' of von Winiwarter and Sainmont ('08). In the case 

 of the former, the suggestion might be ventured that this ap- 



