Development of the Nine-Banded Armadillo. 367 



The pregnant uterus assumes a variety of shapes in different 

 individuals. At approximately the same period of pregnancy it 

 may be either elongated or comparatively broad, either blunt 

 or pointed at one or both ends, and either simple or clearly 

 bilobed dorso-ventrally at the fundus end (figs. 42 and 43). 

 These various forms are not due to the position or arrangement 

 of the foetuses, which in this respect are practically constant, but 

 probably to individual variation influenced by the previous func- 

 tional history of the organ. 



III. NUMBER, ARRANGEMENT AND SEX OF THE 

 EMBRYOS 



A. Number of Embryos 



In sixty-five out of seventy cases there were four normal embryos 

 in a vesicle. It may be assumed then that four is typical for 

 the species. Three atypical conditions occurred which may be 

 listed as follows: 



1. Vesicles containing five normal embryos (three cases, nos. 

 28, 91, 108). 



2. Vesicle containing three normal embryos each measuring 

 15 mm. and one decidedly abnormal embryo 7 mm. in length 

 (no. 57). No doubt this vesicle was destined to produce a three- 

 embryo litter. 



3. A case of twins (no. 137 ). These were born in captivity. 

 A very careful examination of the uterus and intestines of the 

 mother convinced us that there were no other young born. This 

 may have been a case somewhat like the preceding except that 

 two embryos degenerated instead of one. 



There appear not infrequently in otherwise normal embryonic 

 vesicles small amniotic sacs that usually contain the more or 

 less completely degenerated remains of what may once have 

 been extra embryos. In one case (no. 108), a vesicle with five 

 normal 'embryos, such a sac appeared, which, if truly the repre- 

 sentative of an extra embryo, would furnish an example of a six- 



