THE URINOGENITAL SYSTEM. 97 
position. Its gubernacular connections are, however, plainly 
discernible in the adult animal by the ovarian and round liga- 
ments, the latter being inserted into a small pocket of the abdom- 
inal wall simulating the testis sac. 
Though inconspicuous in gross size as compared with the testis, 
the ovary is concerned with the formation of cells of relatively large 
dimensions, the female germ cells or ova. These undergo their 
THE OVARY principal development as single cells in the 
AND OVIDUCTS. tissue of the organ, but at times, through 
rupture of the enclosing follicles, they gain 
access to the surface, and thence pass directly into the open mouth 
of the uterine tube. If fertilized, they begin their segmentation 
and further development into an embryo, the latter becoming 
attached to the wall of the 
uterus. A placental con- 
nection is formed by which 
nourishment is carried to the 
embryo, during the period of 
intra-uterine life, in the rabbit 
aboutchieny days. Wheresare «irene: Avuterus dunies B acerus bcos; © 
mwoleomiplete ter, thevcavis (cue oes oy Seeteae ; tubes us uteris: 
ties of which are connected 
distally with the unpaired vagina, and through this with the 
urinogenital sinus. The size and appearance of the uteri depend 
upon the age of the animals examined, and upon whether or not 
they are pregnant or have borne young. The uteri of pregnant 
females are greatly enlarged and vascular. They contain from five 
to eight young, the position of which may be easily seen from the 
expansion of those parts of the tubes in which they lie. 
The paired condition of the uteri in the rabbit is especially 
instructive because of its primitive nature as compared with that 
in many othermammals. Paired oviducts (Fig. 49A) are the rule 
in lower vertebrates, where the function is simply to carry the 
eggs to the outside of the body, This condition is retained with 

minor modifications to the mototreme stage of mammals, but in 
higher forms of the latter the ducts are successively coalesced. 
In marsupials there are still paired vaginae, while in placentals the 
structure is unpaired. In the rabbit, as in many lower placentals, 
