Figs. 1A, 1B, 1C, 1D. Four sections from a female Scyllium canicula of a
stage between M and N through the part where the segmental duct becomes
split into Wolffian duct and oviduct. Zeiss B, ocul. 2. 1A is the foremost
section.
The sections shew that the oviduct arises as a thickening on the under
surface of the segmental duct into which at the utmost a very narrow
prolongation of the lumen of the segmental duct is carried. The small size
of the lumen of the Wolffian duct in the foremost section is due to the
section passing through nearly its anterior blind extremity.
Fig. 2. Section close to the junction of the Wolffian duct and oviduct in a
female embryo of Scyllium canicula belonging to stage N. Zeiss B, ocul. 2.
The section represented shews that in some instances the formation of the
oviduct and Wolffian duct is accompanied by a division of the lumen of the
segmental duct into two not very unequal parts.
Figs. 3A, 3B, 3C. Three sections illustrating the formation of a ureter in
a female embryo belonging to stage N. Zeiss B, ocul. 2.
3A is the foremost section.
The figures shew that the lumen of the developing ureter is enclosed in
front by an independent wall (fig. 3A), but that further back the lumen is
partly shut in by the subjacent Wolffian duct, while behind no lumen is
present, but the ureter ends as a solid knob of cells without an opening
into the Wolffian duct.
Fig. 4. Section through the ureters of the same embryo as fig. 3, but
nearer the cloaca. Zeiss B, ocul. 2.
The figure shews the appearance of a transverse section through the wall of
cells above the Wolffian duct formed by the overlapping ureters, the lumens
of which appear as perforations in it. It should be compared with fig. 9A,
which represents a longitudinal section through a similar wall of cells.
Fig. 5. Section through the ureters, the Wolffian duct and the oviduct of a
female embryo of Scy. canicula belonging to stage P. Zeiss B, ocul. 2.
Fig. 6. Section of part of the Wolffian body of a male embryo of Scyllium
canicula belonging to stage O. Zeiss B, ocul. 2.
The section illustrates (1) the formation of a Malpighian body (_mg_) from
the dilatation at the end of a segmental tube, (2) the appearance of the
rudiment of the Müllerian duct in the male (_od´_).
Figs. 7_a_, 7_b_. Two longitudinal and vertical sections through part of
the kidney of an embryo between stages L and M. Zeiss B, ocul. 2.
7_a_ illustrates the parts of a single segment of the Wolffian body at this
stage, vide p. 491. The segmental tube and opening are not in the plane of
the section, but the dilated vesicle is shewn into which the segmental tube
opens.
7_b_ is taken from the region of the kidney proper. To the right is seen
the opening of a segmental tube into the body-cavity, and in the segment to
the left the commencing formation of a ureter, vide p. 502.
Fig. 8. Longitudinal and vertical section through the posterior part of the
kidney proper of an embryo of Scyllium canicula at a stage between N and O.
Zeiss A, ocul. 2.
The section shews the nearly completed ureters, developing Malpighian
bodies, &c.
Fig. 9. Longitudinal and vertical section through the anterior part of the
kidney proper of the same embryo as fig. 8. Zeiss A, ocul. 2.
The figure illustrates the mode of growth of the developing ureters.
9A. More highly magnified portion of the same section as fig. 9.
Compare with transverse section fig. 4.
Fig. 10. Longitudinal and vertical section through part of the Wolffian
body of an embryo of Scyllium canicula at a stage between O and P.
The section contains two examples of the budding out of the vesicle of a
segmental tube to form a Malpighian body in its own segment and to unite
with the tubulus of the preceding segment close to its opening into the
Wolffian duct.