No. 3.] UTERUS AND EMBRYO. 353 
where the ectoderm, Fig. 7, Ecto, touches the placenta, the active 
resorption of the degenerated glands is going on (see the part of 
Fig. 7, above bracket C); whereas in other parts the glands pre- 
sent: the appearance shown in Fig. 7, A, gz, and described by 
Masquelin and Swaen. There is also an intermediate zone 
shown in Fig. 7, above bracket B, where the transition phases 
between the two states are found; the zone of transition lies 
immediately underneath the point where the ectoderm, £céo, 
joins the uterine epithelium, /.ef; here the glands are thick- 
ened and hypertrophied ; the lumen is obliterated, but the cylin- 
drical shape is irregularly preserved; where the distal end of the 
ectoderm leaves the placenta, there is again a similar transi- 
tion: in other words, the resorption is less advanced around 
the periphery than in the centre of the area of ectodermal 
attachment. The resorptive process is essentially the same 
as outside the placenta, — superficial corrosion and internal 
vacuolization, — but the vacuoles formed are relatively small 
and consequently more numerous: moreover, the space left by 
the disappearing epithelium is at once occupied by connective 
tissue cells, so that there are no cavities. The resorption goes 
on principally in the superficial layers of the placenta, where it 
results, as later stages show, in the complete disappearance of the 
glands immediately underneath the ectoderm; deeper down the 
glands at the present age are hypertrophied and without lumina, 
but even in the region of bracket C of Fig. 7 (Pl. XX VII.) most 
of the glands show very few or no vacuoles. 
§ 5. Embryo at nine days and three hours. — It is not pro- 
posed to consider here anything but a few points bearing on the 
relations of the embryo to the uterine walls. 
First, as to the fosztion of the embryo: the dorsal surface of 
the embryo is turned towards the placenta; the embryo may be 
situated over one or the other lobe of the placenta or across 
both; its long axis may be either parallel or oblique or at right 
angles, to the long axis of the uterus. In the specimen repre- 
sented in Cut 1, both the uterus and embryo appear in trans- 
verse section. Similar variability appears in my specimens of 
uteri of eight days, and of nine days and seventeen hours. The 
statements of Van Beneden and Julin, 44, and other authors,! 
1 Compare Bischoff, Entwickelungsgesch. d. Kaninchens, p. 138, and von Baer, 
Entwickelungsgesch. i1., 232. 
