OF OECANTHUS AND TELEAS. 



231 



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Fig. 9. 



Fig. 10. 



Fig. 9. An ovarian follicle of 

 Oecantlms in which the germi- 

 native vesicle lies in contact 

 with the surface of the follicular 

 epithelium. 



Fig. 10. Same as Fig. 9. 



the yolk but fades into the nuclear substance on the inner surface. The nucleolus and 

 all other nodules of nuclear filaments or nuclear substance, extend themselves in tbe form 

 of very delicate, tortuous threads which in tbe fresh condition give the vesicle a finely 

 granular appearance. This process continues until the membrane has become so thin as 

 to be indistinguishable in the fresh state. It finally disappears altogether, first at its 

 upper, or sometimes at its outer, surface. (PL 20, fig. 1.) 



Tbe germinative vesicle has in tbe meantime travelled from its 

 central or subcentral position to the surface of the yolk and lies 

 in contact with the follicular epithelium. The use of reagents causes 

 a sharp line of demarkation between the yolk and the nuclear sub- 

 stance to appear in sections of the egg at this stage. This line of 

 condensed protoplasmic substance appears to belong to the yolk. 

 The nuclear substance gradually becomes diffuse in the region of 

 this membrane but remains sharply marked off from the follicular 

 epithelium. The entire nuclear mass now becomes a finely granu- 

 lar homogeneous cloud which spreads out over the surface of the 

 yolk and in this manner disappears from view. (PI. 20, figs. 28 

 29. At the t ime of the disappearance of the germinative vesicle 

 the egg has accpiired about one-half of its yolk substance. The 

 latter is aggregated into an ovoid mass. The egg soon secretes 

 about itself a membrane which at this time is to be detected only by treatment with 

 hardening reagents. 



The process of the formation of the yolk and the egg membranes (save the vitelline 

 membrane) is a continuous phenomenon. By a process of nuclear proliferation, the folli- 

 cular cells are elongated into a very thick columnar layer. (PL 20, figs. 1, 4, 13, 

 14, 18, 20. PL 21, figs. 24, 26.) These cells vary in their radial diameter with the num- 

 ber of nuclei present, and the latter vary from one to four in a single cell. The outer or 

 first nucleus is sharply marked off from the small amount of cell protoplasm surrounding 

 it, while each succeeding nucleus becomes less distinct, until the nuclear outlines are lost in 

 a region of indifferent granular and filamentous substance, with here and there oil 

 globules and bits of album inous matter, distinct from the matrix of degenerated cell mate- 

 rial out of which they have been differentiated by some chemical processes. In the upper 

 follicles where the process is just begun the cells commonly possess two nuclei, and in the 

 last follicle, or the one in which the chorion membranes are being formed, they also pos- 

 sess two, if at the beginning, but if at tbe end of the process, a single, small, degenerated 

 nucleus, surrounded by a cell wall containing a proportionally large amount of a thin, 

 watery protoplasm. In the follicles between these two extremes, where yolk formation is at 

 its height, there maybe as many as four nuclei in a cell, each surrounded hy a proportionally 

 small amount of finely granular protoplasm. The outer nucleus presents the characteristic 

 appearance of a normally active structure, while the inner ones reproduce successively the 

 characters of the degenerate nuclei of the last follicle. Finally, after the chorion is secreted 

 and the egg has passed out into the oviduct, the remains of the follicular epithelium, 

 together with tbe tunica propria, form a contracted mass, — the corpus luteum, — which 



disappears before the next egg makes its way into the oviduct. In pi. 20, 



figs. 



14 -P 



