SECT. XIIT 



PHYLUM CHORDATA 



567 



(A, ut.) remain distinct ; in others their posterior portions coalesce 



(B, C), the anterior parts remaining separate, so that there is formed 



a median corpus 



uteri 



horns 



with 



two 



or cornua. 

 In Primates and 

 some Edentates 

 the coalescence 

 goes still further, 

 there being an 

 undivided uterus 

 (D) in addition to 

 an undivided 

 vagina, the only 

 parts of the ovi- 

 ducts which re- 

 main distinct from 

 one another being 

 the narrow ante- 

 rior parts or Fallo- 

 pian tubes. In all 

 Mammals there is, 

 in the vestibule or 

 urinogenital pas- 

 sage through 

 which the vagina 

 communicates 

 with the exterior 

 by the aperture 

 of the vulva, a 

 small body the 

 cl ito ris the 

 homologue of the 

 penis, and some- 

 times perforated 

 by the urethral 

 canal. 



Development. 

 -The ova of 

 Mammals (Fig. 

 1225), like those 

 of Vertebrates in 

 general, are deve- 

 loped from cer- 



FIG. 1224. Various forms of uteri in Euthcria. A, B, C, D, 

 diagrams illustrating the different degrees of coalescence of 

 the oviducts. A, two distinct uteri. B, bicornuate uterus. 

 C, uterus with a median partition. D, complete 'coalescence. 

 E, female reproductive organs of one of the Mitstelina with 

 embryos (**) in the uterus. F, female reproductive organs of 

 the Hedgehog. B, urinary bladder ; C'e. cervix uteri (neck of 

 uterus) ; N, Nn, kidneys and adrenal bodies ; Od. Fallopian 

 tube ; Ot. ostinm tubae (abdominal opening of Fallopian tube ; 

 r. rectum ; Sin/, urinogenital canal ; Ur. ureter ; Ut. uterus ; Vg. 

 vagina ; ft. accessory glands. (From Wiedersheim's Compara- 

 tive Anatom//.) 



tain cells of the 



germinal epithelium, the primitive ova (pr. ov.). Each of these, 



surrounded by smaller unmodified cells of the epithelium, sinks 



