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. The arms 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 191 1 

 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 this method 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 



