376 



COMPARATIVE MORPHOLOGY OF VERTEBRATES 



Lastly, as in primates (figs. 399, D; 400, V, VI) the fusion is complete 

 and a uterus simplex occurs, the double nature being shown only by 

 the two Fallopian tubes. 



The reproductive duct of the male is the Wolfl&an duct which is 

 connected with the testis by the epididymis already described. 

 There are numerous small tubules, the homologues of the efferent 

 ductules of the lower vertebrates, and like them connected by vessels 

 which correspond to the longitudinal canals. The upper end of the 

 Wolffian duct (now called the vas deferens) is greatly coiled, and the 



k=::i 



Fig. 400. — Dorsal and side views of female genital structures in I, monotreme; 

 //, Orycteropus (uterus duplex); ///, many monodelphs (Uterus bipartitus); /V, most 

 monodelphs; V, Bradypus; VI, Dasypus; b, bladder; cu, urogenital sinus;/, Fallopian 

 tube; g, genital sinus; u, uterus; v, vagina. 



lower portion opens into the urogenital sinus, or urethra, the walls of 

 which are muscular, forming an ejaculatory duct. 



In the female the WolflBan duct and the mesonephros are largely lost in the 

 adult, the mesonephros forming a small collection of tubules near the anterior 

 end of the ovary which are known as the parovarium. In the male the Miillerian 

 duct is also largely lost, the lower portion sometimes persisting as a small bUnd 

 tubule imbedded in the prostate gland and known as the uterus masculinus. 



In the testes, between the tubules, are small aggregates of cells known as 

 interstitial cells, which have recently been shown to be glands with internal 

 secretion. In man their products, which pass into the blood, apparently cause 

 the assumption of the secondary male characters — growth of hair on the face, 

 change of voice, etc. — at the time of puberty. There would also seem to be 



