XII.] GENITAL CORD. 415 



body. The Wolffian duct itself becomes in the male the 

 vas deferens and the convoluted canal of the epididy- 

 mis ; the latter structure except the head being entirely 

 derived from the Wolffian duct. 



The functionless remains of the embryonic organs described 

 for the chick (p. 224) are found also in mammals. 



The Miillerian ducts persist in the female as the 

 Fallopian tubes and uterus. 



The lower parts of the urinogenital ducts are some- 

 what further modified in the Mammalia than the Chick. 



The genital cord. The lower part of the Wolffian 

 ducts becomes enveloped in both sexes in a special cord 

 of tissue, known as the genital cord (Fig. 1 40 gc), within 

 the lower part of which the Mulleriaii ducts are also 

 enclosed. In the male the Miillerian ducts in this cord 

 atrophy, except at their .distal end where they unite to 

 form the uterus masculinus. The Wolffian ducts, after 

 becoming the vasa deferentia, remain for some time 

 enclosed in the common cord but afterwards separate 

 from each other. The seminal vesicles are outgrowths of 

 the vasa deferentia. 



In the female the Wolffian ducts within the genital 

 cord atrophy, though rudiments of them are for a long 

 time visible or even permanently persistent. The lower 

 parts of the Miillerian ducts unite to form the vagina 

 and body of the uterus while the upper become the 

 horns of the uterus and the Fallopian tubes. The 

 junction commences in the middle and extends forwards 

 and backwards ; the stage with a median junction being 

 retained permanently in Marsupials. 



The urinogenital sinus and external generative 

 organs. The dorsal part of the cloaca with the alimen- 



