398 A. A. W. HUBRECHT. 
and embryo rapidly grow. Decidua reflexa and lower half of trophosphere 
commence to thin out. 
Fic. 35.—Allantoidean placenta rapidly developing. Omphaloidean attach- 
ments in trophoblast lost. The trophosphere (in the omphaloidean region) 
and the reflexa are being reduced to thin membranes. The uterus lumen 
penetrates upwards behind the placenta, a new epithelium rapidly originating. 
Fic. 36.—The same, advanced towards its final stage. The yolk-sac has 
ceased to grow, and is reduced and folded against the embryo’s belly. Pla- 
centa more complete; fcetal membranes still further attenuated. After-birth 
on the way of being peeled out by the further extension upwards of the 
uterus lumen and its renovated epithelium. In Figs. 34—36 radial tracts of 
tissue are seen to take their course through the allantoic cavity; embryonic 
vessels entering and leaving the placenta both in the centre and at the border. 
The maternal vessels in the stage of Fig. 36 have to take their course from 
the mesometrium, through the attenuated uterine wall, up to the antimeso- 
metrical region, where they enter the placenta. 
PLATE XX. 
Fic. 37.— Enlarged drawing of part of a section corresponding to the stage 
of Fig 5 and diagram 28. The section not being strictly transverse the lumen 
has not a full T-shape. The lips of the decidua reflexa are as yet far from 
coalescence. In the uterine lumen (Z.) a small blood extravasate (c/.) has 
appeared consequently upon the hemorrhagic cedema (@.), which is at this 
stage always noticed in the above-mentioned lips. A few sections further an 
embryo was situated in the depression (/.) corresponding in development to 
that of Fig. 5. The uterine epithelium, well-preserved on the mesometrical 
side where the tubular glands (g/'.) open out into the lumen, is fairly on the 
way of retrogressive metamorphosis on the opposite side, and in the central 
depression (/.) of the decidual proliferation. The glands in this proliferating 
region are most distinctly seen to undergo a retrograde development. Their 
open mouths (g/.) are closed, their lumen disappears, their constituent cells 
can be distinguished from the surrounding stroma only with difficulty (cf. Fig. 
2). The histological character of that stroma is easily gathered from the 
drawing. The proliferating connective-tissue cells are densely packed. Be- 
tween them vasifactive tissue is everywhere present, and the future blood- 
spaces can as yet only be recognised by the faint trace of a darker endothelium. 
Only here and there actual lumina (ca.) can be detected. These lumina are 
from the beginning so wide that they cannot be compared to ordinary capillaries, 
but must be looked upon asa vascular formation sui generis. (art.) Arterioles 
in the mesometrical region. (Mus. Utr, Cat. n® Erin. 137 a}, 3 7.) 
