562 J. T. PATTERSON 
tion over the lining of the uterus, except at the tip of the fundus, 
where there is a four-pointed, cross-shaped area of rather smooth 
mucosa. Thearms of this cross meet each other at approximately 
right angles, and their common area is the extreme tip of the 
fundus. This cross also indicates the orientation of the uterus; for 
two of the arms mark the dividing line between the upper and 
lower halves of the fundus, and two form a rather broad, shallow 
groove extending from the mid-dorsal point around to the mid- 
ventral point of the uterine cavity. These facts are most clearly 
brought out in an everted uterus (fig. 21). 
Each one of the arms forms a distinct furrow leading from the 
tip of the fundus to the uterine opening of the fallopian tube. As 
already indicated, the other two arms lead from the center of the 
fundus to the middle of the upper and lower surfaces, respectively. 
These usually form shallow furrows which end distally among the 
folds of the mucosa. For convenience we shall speak of the first 
pair as the right and left horizontal grooves, and of the second pair 
as the dorsal and ventral vertical grooves. On account of the fact 
that the uterine openings are situated slightly nearer the fundus 
than the cervix end, the horizontal grooves are somewhat shorter 
than the vertical grooves. 
To the student of the early development of the armadillo, the 
significance and importance of this cross-shaped area can scarcely 
be over emphasized. The right and left horizontal groove forms 
the pathway along which the embryonic vesicle passes on its way 
from the fallopian tube to the tip of the fundus; and the center of 
the cross, or the central area of the fundus, is the attachment zone 
or placental area for the vesicle. The discovery of these facts has 
greatly facilitated the collecting of the early stages. Prior to 1911 
attempts were made to obtain the young stages, and various 
methods were tried, such as that used with great success by Eng- 
lish workers in collecting the early stages, namely, that of inject- 
ing the uterine cavity full of some killing fluid, and later examining 
the contents for the embryos. While thismethod works well where 
one is dealing with an animal which gives off several eggs at each 
ovulation, yet in the case of a single egg at each pregnancy the 
chances of its discovery are few. Furthermore, to any one who 
