Part 19

Fig. 6. Section through the ovarian ridge of an embryo of Scyllium canicula, slightly older than fig. 5. To illustrate the relation of the ovarian epithelium to the subjacent vascular stroma. Zeiss A, ocul. 2. Osmic acid.

Fig. 7. More highly magnified portion of the same ovary as fig. 6. To illustrate the same points. Zeiss C, ocul. 2. Osmic acid.

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 f.e. is seen a surface view of the follicular epithelium of an ovum. Zeiss C, ocul. 2. Picric acid.

Fig. 11. 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, 16, 17, 18 [Figs. 17 and 18 are on Pl. 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. fe. Follicular epithelium. fe´. Secondary follicular epithelium. gv. Germinal vesicle. nn. Nests of nuclei of ovarian region. o. Permanent ovum. pse. Pseudo-epithelium. str. Stroma ingrowths into ovarian epithelium. vt. Vitelline membrane. x. Modified nucleus. yk. Yolk (vitellus). zn. Zona radiata.

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, containing 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 (f.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.

Fig. 24. Fully formed ovum containing a second nucleus (x), probably about to be employed as pabulum; from the same ovary as fig. 5. The follicular epithelium is much thicker on the side adjoining the stroma than on the upper side of the ovum. Zeiss F, ocul. 2. Osmic acid.

Fig. 25. A. Ovum from the same ovary as fig. 21, containing in the yolk three peculiar bodies, similar in appearance to the two small bodies in the germinal vesicle. B. Germinal vesicle of a large ovum from the same ovary, containing a body of a strikingly similar appearance to those in the body of the ovum in A. Zeiss E, ocul. 2. Picric acid.

Fig. 26. Section of the ovary of a young female of Scyllium stellare 16-1/2 centimetres in length. The ovary is exceptional, on account of the large size of the stroma ingrowths into the epithelium. Zeiss C, ocul. 2. Osmic acid.

Fig. 27. Ovum of Scyllium canicula, 5 mm. in diameter, treated with osmic acid. The figure illustrates the development of the yolk and a peculiar mode of proliferation of the germinal spots. Zeiss A, ocul. 2.

Fig. 28. Small part of the follicular epithelium and egg membranes of a somewhat larger ovum of Scyllium canicula than fig. 22. Zeiss D D, ocul. 2.

Fig. 29. The same parts as in fig. 28, from a still larger ovum. Zeiss D D, ocul. 2.

Fig. 30. Ovum of Raja with follicular epithelium. Zeiss C, ocul. 2.

Fig. 31. Small portion of a larger ovum of Raja than fig. 30. Zeiss D D, ocul. 2.

Fig. 32. Follicular epithelium, &c., from an ovum of Raja still larger than fig. 31. Zeiss D D, ocul. 2.

Fig. 33. Surface view of follicular epithelium from an ovum of Raja of about the same age as fig. 33.

Fig. 34. Vertical section through the superficial part of an ovary of an adult Raja to shew the relation of the pseudo-epithelium to the subjacent stroma. Zeiss D D, ocul. 2.