SERIES D. Sections chosen at intervals from a complete series traversing
the peritoneal opening of the Müllerian duct, the remnant of the
head-kidney, and the termination of the Müllerian duct. Zeiss C, ocul. 3
(reduced one-third).
Nos. 1 and 2. Sections through the persistent anterior opening of the
head-kidney (abdominal opening of Müllerian duct). The approach of the
Wolffian duct to the groove may be seen by a comparison of these two
figures. In the sections in front of these (not figured) the two are much
more widely separated than in No. 1.
No. 3. Section through the Müllerian duct, just posterior to the persistent
opening.
Nos. 4 and 5. Remains of the ridges, which at an earlier stage connected
the first and second grooves, are seen passing from the Müllerian duct to
the peritoneal epithelium.
No. 6. Rudiment of the second groove (_gr_2.) of the head-kidney.
Between 6 and 7 is a considerable interval.
No. 7. All traces of this groove (_gr_2.) have vanished, and the Müllerian
duct is quite disconnected from the epithelium.
No. 8. Rudiment of the third groove (_gr_3.).
No. 9. Müllerian duct quite free in the space between the peritoneal
epithelium and the Wolffian duct, in which condition it extends until near
its termination. Between Nos. 9 and 10 is an interval of eight sections.
No. 10. The penultimate section, in which the Müllerian duct is seen. A
lumen cannot be clearly made out.
No. 11. The last section in which any trace of the Müllerian duct is
visible. No line of demarcation can be seen separating the solid end of the
Müllerian duct from the ventral wall of the Wolffian duct.
FIGS. E. and F. Sections through the glomerulus of the head-kidney from an
embryo prior to the appearance of the head-kidney. Zeiss B, ocul. 2. A
comparison of the two figures shows the variation in the thickness of the
stalk of the glomerulus. E. Section anterior to the foremost Malpighian
body. F. Section through both the glomerulus of the head-kidney and that of
a Malpighian body. The two are seen to be connected.
SERIES H. Consecutive sections through the hind end of the Müllerian duct,
from an embryo in which the head-kidney was only represented by a rudiment.
(The embryo was, perhaps, very slightly older than that from which Series D
was taken.) Zeiss C, ocul. 3 (reduced one-third).
No. 1. Müllerian duct is without a lumen, and quite distinct from the
Wolffian wall.
No. 2. The solid end of the Müllerian duct is no longer distinct from the
internal wall of the Wolffian duct.
No. 3. All trace of the Müllerian duct has vanished.
SERIES I. Sections through the hinder end of the Müllerian duct from an
embryo of about the middle of the sixth day. Zeiss C, ocul. 2 (reduced
one-third).
No. 1. The Müllerian duct is distinct and small.
No. 2. Is posterior by twelve sections to No. 1. The Müllerian duct is
dilated, and its cells are vacuolated.
No. 3. Penultimate section, in which the Müllerian duct is visible; it is
separated by three sections from No. 2.
No. 4. Last section in which any trace of the Müllerian duct is visible;
the lumen, which was visible in the previous section, is now absent.
No. 5. No trace of Müllerian duct. Nos. 3, 4, and 5 are consecutive
sections.
FIG. K. Section through the hind end of the abdominal opening of the
Müllerian duct of a chick of 123 hours. Zeiss C, ocul. 2 (reduced
one-third). It illustrates the peculiar cord connecting the Müllerian and
Wolffian ducts.