_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.
[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,
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 canicul_a 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.