206 DR. F. WOOD-JONES ON THE 
canal communicating with the uterus does not usually become 
established as a permanency in the mole, but the experience of 
meeting with one winter female with a patent vagina would 
make me prepared to believe that at times the communication 
may be permanently established. We have in this process a 
most remarkable parallel to the evolution of the medina vagina 
of the Marsupials, to which reference will be made later. 
Text-figure 10, 
Winter female with a perineal orifice (Dec. 5th). Second year. 
D. Embryonic Stages of Internal Genitalia. 
In order to follow the embryonic development of the female 
genital ducts and orifices, I have been compelled to prepare a 
very large series of sections, for the difficulty of distinguishing 
the sexes during embryonic life renders the selection of material 
exceedingly difficult. The female ducts have been followed 
in their entire length in embryos of 27 mm, and 33 mm. 
respectively. 
In the earlier of these stages the arrangement of the ducts is 
comparatively simple, for in the female, just as in the male, the 
genital ducts end separately in the floor of the closed uro-genital 
