POLYEMBRYONIC DEVELOPMENT IN TATUSIA 563 
has endeavored to study the fragile mammalian vesicle, the diffi- 
culty of preserving the delicate structure even after discovery, is 
indeed very great. 
Early in the fall of 1911, however, the real significance of the 
cross-shaped grooves, and especially of the horizontal one, was 
first fully realized, and since then not much difficulty has been ex- 
perienced in obtaining the free uterine or early attached vesicles. 
In the living or fresh uterus it can easily be demonstrated that the 
horizontal groove of each side is virtually a tube, and is therefore, 
a continuation of the fallopian tube. This is brought about by 
the depth of furrow and by the depressed condition of the uterus 
dorso-ventrally. 
The best method to follow in seeking to obtain a young vesicle 
is to cut the uterus along each side in the plane of the broad liga- 
ment, beginning at the cervix and extending to a point lying a 
short distance from the opening of the fallopian tube, and then 
slowly to evert the fundus portion over the end of the small finger. 
By this procedure the horizontal furrows are spread wide open, 
and the vesicle, if present, will be revealed. The tip of the everted 
uterus is then applied to the killing fluid and the vesicle, if not 
attached, will float out on the surface of the fluid, and after afew 
seconds slowly sink to the bottom without distortion. In the case 
of attached vesicles, the everted uterus is placed in the fluid, and, 
after fixation and hardening is affected, a properly oriented block 
containing the vesicle is cut out of the mucosa. The process of 
obtaining these early free stages may be greatly facilitated by 
first determining which ovary holds the corpus luteum, and confin- 
ing one’s search to the corresponding horizontal groove. 
NOTES ON BREEDING HABITS 
1. General statement 
During the past five years a considerable amount of informa- 
tion concerning the habits of this animal has been secured by the 
writer, and it may be worth while eventually to publish these ob- 
servations; but here I wish merely to make a few remarks on cer- 
tain phases of the breeding habits. 
