456 



COMPARATIVE ANATOMY 



primitive condition is also seen in the mesonephros, which consists 

 of long, narrow, varicose bands, usually extending from the heart 

 to the anterior part of the cloaca, which latter is often much 



ffv. ^ 



/fffefj 



m 



FII;. 342. DIAGRAM OF THE URINOGENITAL SYSTEM OF (A) A MALE AND (B) 

 A FEMALE UKODELE ; FOUNDED ON A PREPARATION OF Triton tuninttt* 

 (After J. W. Spengel.) 



a, collecting tubes of the mesonephros, which open into the Wolffian (urino- 

 genital) duct (Ig) ; in the female the latter serves simply as the urinary 

 duct (Ur), and the system of the vasa efferentia (testicular network) is 

 vestigial ; ON, anterior portion of kidney (epididymis of the male) ; 

 Ho, testis ; mg, mg\ Miillerian duct ; N, posterior non-sexual portion of 

 kidney ; Of, cn-lomic aperture of Miillerian duct (oviduct, Od) ; Or, ovary ; 

 Ve, vasa efferentia of testis which open into the longitudinal canal of the 

 mesonephros, f. 



elongated. In the embryo they consist of definite masses which 

 are arranged metamerically, and in each of them a glomerulus, a 

 nephrostome, and an excretory duct can be distinguished (Fig. 



