_dn._ Modified nucleus of primitive ovum. _do._ Permanent ovum in the
act of being formed. _dv._ Developing blood-vessels. _dyk._ Developing
yolk. _ep._ Non-ovarian epithelium of ovarian ridge. _fe._ Follicular
epithelium. _gv._ Germinal vesicle. _lstr._ Lymphatic region of stroma.
_n n._ Nests of nuclei of ovarian region. _o._ Permanent ovum. _ovr._
Ovarian portion of ovarian ridge. _po._ Primitive ovum. _ps e._
Pseudo-epithelium of ovarian ridge. _str._ Stroma ingrowths into ovarian
epithelium. _v._ Blood-vessel. _vstr._ Vascular region of stroma
adjoining ovarian ridge. _vt._ Vitelline membrane. _x._ Modified
nucleus. _yk._ Yolk. _zn._ Zona radiata.
Fig. 1. Transverse section of the ovarian ridge of an embryo of _Scy.
canicula_, belonging to stage P, shewing the ovarian region with
thickened epithelium and numerous primitive ova. Zeiss C, ocul. 2.
_Picric acid._
Fig. 2. Transverse section of the ovarian ridge of an embryo of
_Scyllium canicula_, considerably older than stage Q. Zeiss C, ocul. 2.
_Picric acid._ Several nests, some with distinct ova, and others with
the ova fused together, are present in the section (_nn_), and several
examples of modified nuclei in still distinct ova are also represented.
One of these is marked _x_. The stroma of the ovarian ridge is
exceptionally scanty.
Fig. 3. Transverse section through part of the ovarian ridge, including
the ovarian region of an almost ripe embryo of _Scyllium canicula_.
Zeiss C, ocul. 2. _Picric acid._ Nuclear nests (_n.n._), developing ova
(_d.o._), and ova (_o._), with completely formed follicular epithelium,
are now present. The ovarian region is still well separated from the
subjacent stroma, and does not appear to contain any cells except those
of the original germinal epithelium.
Fig. 4. Section through ovarian ridge of the same embryo as fig. 3, to
illustrate the relation of the stroma (_str._) and ovarian region. Zeiss
_a a_, ocul. 2. _Picric acid._
Fig. 5. Section through the ovarian ridge of an embryo of _Scyllium
canicula_, 10 cm. long, in which the ovary was slightly less advanced
than in fig. 3. To illustrate the relation of the ovarian epithelium to
the subjacent vascular stroma. Zeiss A, ocul. 2. _Osmic acid._ _y._
points to a small separated portion of the germinal epithelium.
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._