BY JAS. P. HILL. 51 



Vaginae. 



Vaginal creca.-— Posteriorly, as has been described above, the 

 vaginal cjeca are closely united to the uterine necks above and to 

 the fundus of the bladder below, but anteriorly they become quite 

 free and form a large bilobed sac (up to 4"5 cm. in length) with 

 thin semi-ti'ansparent walls lying between the uteri above and 

 the bladder below, and greatly exceeding either in size (Plate i., 

 figs. 1 and 2,vag.c.). The caeca are separated from each other by 

 a common median partition wall and each is directly continuous 

 behind with the corresponding lateral vaginal canal, of which it 

 simply forms a forward expansion. The Cc^ca are lined by a layer 

 ■of columnar epithelium which has usually a ridged appearance in 

 surface view (fig. 2, vag.c). 



The vaginal caeca function as receptacula seminis. Of this I 

 have been able to satisfy myself through the capture of a female 

 specimen of P. obesula apparently just after an act of coitus. The 

 uteri were slightly enlarged and congested, while the cfeca were 

 greatly dilated and filled by a clear viscid semifluid material 

 together with masses of hard, opaque, caseous-looking substance 

 of an albuminous nature. Microscopic examination of the viscid 

 material revealed the presence of abundant spermatozoa with 

 somewhat oblong heads pointed anteriorly and measuring -005 mm. 

 in length by •002 mm. in breadth, and with tails averaging '15 mm. 

 in length {cf. 8, p. 312). Usually the cteca contain only the hard, 

 opaque material which is essentially similar to the " inspissated 

 secretion commonly present both in the cul-de-sac and the lateral 

 vaginal canals " of Macropus according to Owen (8) and noted 

 by various observers from Home (14) onwards. According to 

 Owen (9) these masses "most resemble those coagulated masses 

 that are found in the vesiculae seminales and sometimes in the 

 urethra of the Agouti, Capromys, Guinea-pig and others of the 

 Rodent order." Without doubt these hard masses are derived 

 from the same source, viz., from the secretion accompanying the 

 spermatozoa. 



In certain species of Kangaroo Rats of the genus Potorous there 

 are present, as described by Owen (9) and Brass (4), forward 



