PLATE XII. 



Fig. 1.— a longitudinal section through the ovaries of a young Lycosa, showicg 

 the posterior ends of these organs as they lie in the body cavity. The ovary 

 is a hollow cylinder lined with epithelial cells, a, and covered with a layer of 

 muscular cells, h. At several points along the tube can be seen numerous 

 cells projecting from the wall and almost, or quite, filling the lumen of the 

 tube. These are the germ-cells which have differentiated from the epithelial 

 lining; c, the very early oogonia, as yet scarcely differentiated; d, oogonia 

 in the spireme stage; e, o5gonia in the spireme stage and one oocyte; /, fol- 

 licular oocytes, or those which have pushed through the wall upon the ex- 

 terior of the tube. 



Fig. 2.— Oogonia dividing to form the oocytes. Though small and embedded in 

 the cells of the ovarian wall, these division figures are easily distinguished by 

 their clearness as compared with the granular appearance of the surround- 

 ing cells. 



Figs. 3, 4, 5. — Greatly enlarged oogonia, showing the formation of the spireme. 



Fig. 6.— a small portion of the ovarian wall, showing three oocytes, a, pushing 

 their way through the epithelial lining, h; c, a well-developed oocyte upon 

 exterior of ovary. 



Fig. 7.— Portion of ovarian wall, showing muscle cells, a, and epithelial cells, b. 

 Numerous oogonia, c, in the spireme stage surround the oocyte, d. It is 

 probable that this cell is no older than the sister cells among which it lies, 

 but on account of some advantage in food supply has developed in advance 

 of them. 



Fig. 8.— Two oocytes, a and b, lying against the ovarian wall, e, showing the 

 relatively large size of the nucleus at this stage and its scattered masses of 

 chromatin. 



Fig. 9.— a follicular oocyte, showing the large germinal vesicle, a, and the vitel- 

 line body, 6, indenting its membrane. The fine granular area, c, is the vitel- 

 line zone in which lies much food material. The outer reticular area, d, is 

 the cytoplasm. Comparing this figure with /, figure 1, we see the growth 

 the egg makes as it nears maturity. 



