308 G. CARL HUBER 
readily accomplished than in those obtained during the preceding 
day. Of the 59 vesicles of this stage obtained, many show ex- 
cellent fixation. The thin wall of the vesicle is no longer so prone 
to fold as in the preceding stage, and does not readily retract 
from the uterine epithelium or mucosa, no doubt owing to a 
distinct adhesion of vesicle wall to the maternal tissue. It is 
dificult, however, so to orient the vesicles as to obtain sections 
of a desired plane. The general position of a given vesicle is 
readily determined, since the enlargement of the uterus marking 
its location is very evident. The vesicles are located in approx- 
imately cylindrical cavities, known as decidual crypts, which 
are directed toward the antimesometrial border. 
These decidual crypts communicate with the lumen of the 
uterus, which lies eccentric and nearer the mesometrial border, 
by means of funnel-shaped openings. The decidual crypts or 
cavities are still lined with uterine epithelium, though this is 
now much flattened in the immediate vicinity of the vesicle 
and may be found in part separated from the mucosa of this 
region. The vesicles are now so placed that in all of them, the 
thicker portion, the floor of the blastodermic vesicles of younger 
stages or region of the germinal disc, is directed toward the 
mesometrial border, thus toward the still patent lumen of the 
uterus, while the roof of the vesicles is directed toward the an- 
timesometrial border, thus toward the bottoms of the decidual 
erypts. The general direction of the decidual crypts is in the 
main at right angle to the long axis of the uterine horn, and 
directed from the mesometrial to the antimesometrial border. 
They may deviate, however, from the general direction at 
various angles and in almost any direction. The decidual crypts 
as seen in cross section do not as a rule present a circular outline, 
but appear as slightly compressed from side to side, having thus 
an oval outline as seen in cross section, with the long axis of this 
oval space as seen in cross section approximately parallel to the 
long axis of the uterine horn. Since the direction of the decidual 
crypts can in uncut material be only approximated, the obtaining 
of sections cut in a desired plane becomes largely a matter of 
chance. In a large number of my preparations the contained 
