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LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



b) Female: The ovaries are masses of connective tissue containing the developing eg( 

 each egg surrounded by a capsule of nutritive cells forming a follicle. The ovaries, unlike t 

 testes, never have any connection with the kidneys. The ducts of the ovaries are named t 

 oviducts or MMerian ducts. The origin of the Miillerian ducts is somewhat problematic; 

 In elasmobranchs they arise by a splitting of the pronephric duct; half of the pronephi 

 duct then becomes the oviduct, and the other half becomes the mesonephric duct. I 

 though this mode of origin is the one commonly accepted, it cannot be demonstrated f 

 other vertebrates; in them the oviducts arise independently in the mesomere. The oviduc 

 are never directly connected with the ovaries. They open into the coelom near the ovar: 



uterine tube 



vagina 

 urethra 



urogenital sinus 



— uterine tube 





/ YL^ vagina 



I IJx urethra 



D E 



Fig. 63. — Diagrams to show the various types of mammalian oviducts. A, condition found 

 the majority of female vertebrates; the two oviducts are completely separate and open independen 

 into the cloaca. B-E, various conditions found in mammals, showing differentiation of the ovidu 

 into uterine tube, uterus, and vagina, and progressive fusion of the lower parts of the oviducts: B, dui 

 type found in rodents, in which the two vaginae are united to one; C, bipartite type occurring in cai 

 vores; not only are the vaginae fused but the lower parts of the two uteri are fused to form a sir 

 body, divided in two by a partition which represents the fused walls of the two uteri; the upper part! 

 the two uteri remain separate as the horns; D, bicornuate type, found in many ungulates, similar t 

 except that the partition has disappeared; E, simplex type, occurring in man and the apes, in wr. 

 both vaginae and uteri are fused along their entire lengths leaving only the uterine tubes separi 

 Note further that in B-D the urethra joins the vagina to form the urogenital sinus which opens 

 the exterior, while in E the urethra and vagina are wholly separate and open independently to 

 exterior. (From Wiedersheim's Comparative Anatomy of Vertebrates, courtesy of the Macmil 

 Company.) 



by a funnel-shaped opening, the ostium, which probably represents one or more of the nepr 

 stomes of the pronephros (Fig. 62 B and D). The eggs escape from the ovary by ruptun 

 the ovarian wall, pass into the ostium of the oviducts by methods which are not always unc 

 stood, and are conveyed down the oviducts. 



The oviducts in the majority of vertebrates remain as two separate tubes opening i 

 the cloaca (Fig. 63^4). In mammals each oviduct is differentiated into a narrower ante 

 portion called the uterine or Fallopian tube, which bears the ostium, and a wider more musci 

 posterior portion, the uterus. In the monotremes, or egg-laying mammals, each uterus op 

 separately into the cloaca. In the marsupials the terminal portion of the uterus is differentia 



