104 



HUMAN EMBRYOLOGY AND MORPHOLOGY. 



their blind extremities in glomeruli. The tubules open into 

 the Wolffian duct just as in the frog; the duct is situated 

 in the basal or attached part of the ridge. It runs back- 



intermediate 

 cell-mass. 



Wolffian body 

 genital gland 

 gut. 



Fig. 80. Diagrammatic section to show the position of the Wolffian and Genital 



Ridges on the dorsal wall of the abdomen. 



wards in this ridge and turns into the pelvis to end with the 

 Miillerian duct (also situated in the Wolffian ridge) in the cloaca 

 of the hind gut. The whole arrangement is similar to that seen 

 in the frog. Further, as in the frog (Fig. 79), the anterior or 

 genital tubules are connected with the genital glands, and are not, 

 as the posterior are, secretory in nature. If the testis were 

 functional at this time — which it is not — the spermatozoa and 

 urine of the Wolffian body would pass to the cloaca by the 

 Wolffian duct. 



Origin of the Wolffian Duct and Tubules. — The tubules 

 which compose the Wolffian body are developed in the inter- 

 mediate cell mass (Fig. 85). At first they are minute transverse 

 vesicles formed by mesoblastic cells in the intermediate mass ; 

 these vesicles become tubular ; one end opens into the Wolffian 

 duct ; at the other a glomerulus is developed. 



The origin of the duct has been traced by Kollmann from the 

 epiblast. It arises on the lateral surface of the body by an 



