6 18 



Comparative Morphology of Chordates 



Oviduct 

 ~ Uterus 



Vagina 



Fig. 490. Four types of uteri. (A) Duplex: in rodents. (B) Bipartite: in certain 

 carnivores. (C) Bicornate: in most insectivores and prosimians. (D) Simplex: 

 characteristic of primates. (After Wiedersheim. Courtesy, Patten: "Embryology 

 of the Pig," Philadelphia, The Blakiston Company.) 



carnivores; ruminant ungulates, pigs, horses). Complete union of right 

 and left uterine chambers to form a single wide and undivided uterine 

 space produces the uterus simplex (in monkeys, apes, and man). 

 In marsupials the egg is fertilized and transported through a 

 Fallopian tube into a uterine region of the oviduct, but no placenta or, 

 at most, a very transitory and weakly developed placenta is formed. 

 The period of gestation is short and the fetus is born while still quite 

 small. The uterus is therefore much less strongly developed than in 

 placental mammals. As to the vaginal regions of the oviducts, there are 

 various conditions. Each duct differentiates a vaginal region. In the 

 opossum (Didelphys: Fig. 491), the two vaginas remain quite separate, 

 although their anterior regions bend sharply toward the median plane 

 and lie close together, while posteriorly they open independently into 

 the urinogenital sinus. In other cases (e.g., kangaroo, phalanger, 

 wombat: Fig. 491) the anterior regions of the right and left vaginal 

 tubes become joined to form a median chamber into which the I wo 

 uteri open, and from this median chamber a pouch (vaginal cecum) 

 projects backward between the separate posterior right and left 

 vaginal tubes. A median longitudinal septum more or less completely 



