OF THE VERTEBRATE OVARY. 615 



Fig. 8. Section through the ovarian region (close to one extremity, where it is 

 very small) from a young female of Scy. canicula. Zeiss C, ocul. 2. Picric acid. It 

 shews the vascular ingrowths amongst the original epithelial cells of the ovarian 

 region. 



Fig. 9. Section through the ovarian region of the same embryo as fig. 8, at its 

 point of maximum development. Zeiss A, ocul. 2. Picric acid. 



Fig. 10. Section through superficial part of the ovary of an embryo, shewing 

 the pseudo-epithelium ; the cells of which are provided with tails prolonged into the 

 general tissue of the ovary. At/, e. is seen a surface view of the follicular epithelium 

 of an ovum. Zeiss C, ocul. 2. Picric acid. 



Fig. 1 1 . Section through part of an ovary of Scyllium canicula of stage Q, with 

 three primitive ova, the most superficial one containing a modified nucleus. 



Fig. 12. Section through part of an ovary of an example of Scyllium canicula, 

 8 cm. long. The section passes through a nest of ova with modified nuclei, in which 

 the outlines of the individual ova are quite distinct. Zeiss E, ocul. 2. Picric acid. 



Fig. 13. Section through part of ovary of the same embryo as in fig. 5. The 

 section passes through a nest of nuclei, with at the least two developing ova, and also 

 through one already formed permanent ovum. Zeiss E, ocul. 2. Osmic acid. 



Figs. 14, 15, 1 6, 17, 1 8 [Figs. 17 and 18 are on PI. 25]. Sections through parts 

 of the ovary of the same embryo as fig. 3, with nests of nuclei and a permanent ova 

 in the act of formation. Fig. 14 is drawn with Zeiss D D, ocul. 2. Figs. 15, 16, 

 17, with Zeiss E, ocul. 2. Picric acid. 



PLATE 25. 



LIST OF REFERENCE LETTERS. 



do. Permanent ovum in the act of being formed, dyk. Developing yolk. J e. 

 Follicular epithelium, f e'. Secondary follicular epithelium, g v. Germinal vesicle. 

 nn. Nests of nuclei of ovarian region, o. Permanent ovum. pse. Pseudo epithelium. 

 sir. Stroma ingrowths into ovarian epithelium, vt. Vitelline membrane, x. Modified 

 nucleus, yk. Yolk (vitellus). z n. Zona radiata. 



[Figs. 17 and 18. Vide description of Plate 24.] . 



Fig. 19. Two nuclei from a nest which appear to be in the act of division. From 

 ovary of the same embryo as fig. 3. 



Fig. 20. Section through part of an ovary of the same embryo as fig. 6, contain- 

 ing a nest of nuclei. Zeiss F, ocul. 2. Osmic acid. 



Fig. 21. Ovum from the ovary of a half-grown female, containing isolated deeply 

 stained patches of developing yolk granules. Zeiss B, ocul. 2. Picric acid. 



Fig. 22. Section through a small part of the ovum of an immature female of 

 Scyllium canicula, to shew the constitution of the yolk, the follicular epithelium, and 

 the egg membranes. Zeiss E, ocul. 2. Chromic acid. 



Fig. 23. Section through part of the periphery of a nearly ripe ovum of Scy. 

 canicula. Zeiss C, ocul. 2. It shews the remnant of the vitelline membrane (v. t.) 

 separating the columnar but delicate cells of the follicular epithelium (/ e.) from the 

 yolk (yk.). In the yolk are seen yolk-spherules in a protoplasmic network. The 

 transverse markings in the yolk-spherules have been made oblique by the artist. 



