1910-11.] Development of Germ Cells in Mammalian Ovary. 163 
consists of a row of cubical cells arranged at right angles to the underlying 
cells. These cells are larger, and contain oval nuclei, which stain more 
deeply than the cells underneath. The chromatin is arranged in masses, 
one mass being larger than the others — the nucleolus. There are a few 
chromatin filaments scattered through the nucleus. The underlying cells 
are of the type of the oogonia and contain pale nuclei, with chromatin 
masses, short filaments, and a nucleolus. The chromatin granules are in 
contact in places with the nuclear membrane, giving it a more marked 
appearance. (Fig. 4.) The cytoplasm of the superficial layer is granular, and 
at the cell junctions there is a deeper stained portion, resembling the “glia ” 
substance or intercellular cement described by Reid (20) in the epithelial 
cells of the cornea. The stroma cells have reached the capsular epithelium 
in places, and are separating it from the underlying tissue. (Fig. 5.) 
Underneath the capsular layer are masses of oogonia filling up the interstices 
between the cell nests, and having stroma cells scattered through them. 
Among the oogonia are numerous more spherical cells, which seem to be in 
a stage transitory between the oogonia and the oocytes of the first order, 
and which correspond to the “ noyaux poussieroides ” of v. Winiwarter and 
Sainmont. The larger spherical clear cells are well seen in these sections ; 
some are just underneath the capsular layer, but the majority are within 
the cell nests. (Fig. 6.) The transition from the oogonium to the first 
oocyte stage (deutobroque) seems a prolonged process. The nucleus becomes 
spread over with fine filaments intersecting each other ; these filaments 
increase in length and thickness until all the chromatin of the granules is 
taken up by the filaments, when we have the typical chromatin reticulum 
in the clear nucleus. In some nuclei the chromatin adheres to the 
membrane and to the filaments as granules, giving them a beaded appear- 
ance. The nucleolus is well marked, and several accessory nuclei are seen. 
Towards the medullary portion, but also just underneath the capsular layer, 
are seen enormous clear nuclei about three to four times the size of the first- 
stage oocyte. (Fig. 7.) These giant nuclei are usually solitary, but some- 
times appear in clusters of three of varying size ; they contain a large, well- 
defined nucleolus, and irregular masses of granular chromatin arranged 
around the nuclear membrane and near the nucleolus. These large nuclei 
seem to correspond to the resting stage of the cell, as described by Berghs in 
plants. After the first or somatic mitosis of the oogonium the cell remains 
in a resting stage, and then begins to take on the characters of the cell 
undergoing heterotypical division (prophase). These large cells may be a 
storehouse for chromatin for future chromosome formation. On the other 
hand, it may be a cell undergoing degenerative changes, becoming swollen 
