Development of the Nine-Banded Armadillo. 365 



non of germ layer inversion is also (indissolubly) bound up with poly- 

 embryony and in turn involves many peculiar and interesting 

 relations. 



Any adequate treatment of the principal problem will therefore 

 necessitate the presentation of a somewhat complex array of 

 facts whose combined verdict will, we trust, establish our main 

 contention. 



Except in the case of the two earliest stages described no at- 

 tempt is made to present a detailed account of the organogeny of 

 the species. No doubt such a study would reveal many facts 

 of interest to the specialist in mammalian embryology, but would 

 serve only to cloud the main issue with obscuring details. 



II. THE FEMALE GENITALIA 



The uterus is simple and not unlike that of the primates in 

 form. In the non-pregnant condition it varies somewhat in size 

 and shape according to the previous history of the individual. 

 In old females that have produced a number of litters the organ 

 though non-pregnant may be distended to several times its normal 

 size, often leading the observer into the vain hope of finding the 

 earliest stages. The uterus of the virgin adult presents a less 

 modified condition and will furnish a basis for the accompanying 

 detailed description. 



The average dimensions of the non-pregnant uterus are as fol- 

 lows : 13 mm. from the tip of the fundus to the junction of the cer- 

 vix with the vagina, 15 mm. between the points of entrance of 

 the* two fallopian tubes, and 10 mm. deepdorso-ventrally. Viewed 

 from the dorsal aspect the uterus appears to be broadly kite- 

 shaped (fig. 7) with the posterior angle blending into the vagina. 

 The fallopian tubes are approximately straight where they enter 

 the uterus, but near the ovaries are strongly convoluted, each 

 ending in a hood-shaped fimbriated infundibulum, which, with 

 the aid of a posteriorly directed flap of the broad ligament, 

 covers a large part of the ovary and thus renders the escape of 

 the ovum into the body-cavity well-nigh impossible. The points 



