| OCR Text |
Show 514 MR. F. E. BEDDARD ON THE DEVELOPMENT AND [D one cell thick, but the nuclei of its constituent cells are so crowded together that it is not easy to be certain upon this point. The outlines of the follicular cells are in many places plainly visible, and irregular processes (Plate LIII. fig. 6 ) project from these cells toward the interior of the mass. This may very well be owing to the shrinking of the central mass of cells', and the consequent breaking away of its connection with the peripheral epithelium. A comparison of the complete series of sections through the developing ovum (the section fig. 6 is towards the middle of the series) shows that, whether or not there is a connection between the entire periphery of the central cells and the follicular epithelium, there certainly is such a connection throughout a limited area lying on that side of the ovum which is nearest the external surface of the ovary, a little above (or below) the pedicle which unites the germinal epithelium with the ovum. In this region the nuclei were more abundant and crowded together than in the central cells of the mass, and were of uniform size and rounded form ; in fact they show an exact similarity to the nuclei of the follicular epithelium, which in this stage, as already mentioned, forms a distinct layer. The mass of cells which connects the follicular layer with the central cells is therefore closely similar to the follicular layer, and has the appearance of a proliferation and growth inwards of that layer. The central cells, as in the previous stage, have nuclei of varying size ; some are long and oval, and others shorter and more spherical; the latter resemble in every particular the nuclei of the surrounding follicular layer. A characteristic feature of this stage is the commencing formation of yolk, which is visible here and there (figs. 27-31) in the cells of the central mass, and in the form of droplets of homogeneous appearance and varying size. This formation of yolk is not confined to the central cells, but is recognizable also in the cells which make up the follicular layer. Here and there among the central cells are homogeneous masses, evidently the same as those referred to in the description of Stage I. as a probable resultant of the breaking-down and fusion of certain of the central cells. These masses were, however, m u c h less developed than in the earlier stage. This stage is evidently, from the facts above narrated, in a further condition of development than that which I have termed Stage I. ; this is also shown in the gradually-advancing separation of the peripheral layers from the germinal epithelium of the ovary. In the earlier stage the pedicle which unites the epithelial layers with the germinal epithelium on the surface of the ovary is not only very thick, but composed almost entirely of germinal epithelial cells in a state of active multiplication. The stroma of the ovary had barely penetrated into this mass of invaginated germinal cells. In Stage II. the body is just as near to the surface of the ovary, and there is a shallow depression on the surface of the ovarv corresponding in position to the centre of the pedicle of attachment, which would appear to be the remains of the invagination of the germinal epithelium. The activity of the germinal epithelium has, however, |
