312 



COMPARATIVE ANATOMY. 



FIG. 244. MALE URINOGENITAL APPARATUS OF THE STURGEON. 

 N, N 1 , N 2 , the different portions of the kidneys ; SG, S&, SGP, the different parts 

 of the ducts of the kidneys ; Vd, Vd\ Vd?, -vas deferens ; Ho, testis : 

 Ve, Ve, network of the vasa efferentia ; MG, Miillerian. duct, which unites with 

 the collecting duct of the kidneys at MG 1 ; t, point at which the two collecting 

 ducts of the kidneys unite, 



development. 1 Posteriorly, the oviducts open into the cloaca 

 somewhat behind the apertures of the ureters -either separately, 

 or by a common canal. 



1 The greater number of Sharks are viviparous. (Concerning the umbilical 

 placenta found in Mustelus Irevia and Carcharias, comp. p. 12.) 



The embryos of Mustelus antarcticus are provided with membranes which bear 



