URIJSrOGENITAL ORGANS 



349 



h. SPECIAL PART. 



Urinary Organs. 



In Amphioxus a series (90 or more) of independent segmental 

 tubules are present on either side in the reduced section of the 

 coelome situated on the dorsal side of the pharynx (" dorsal 



•Savik 



B 



A 



Fill. '277. — Di.\(iR.uiJMATic Tk.vnsversk Suctions through A, Ajiphioxus, in 



THE Br.\N(1HUL REfilON, AND B, AN ElASMOBEANCH EmBRYO, RASED ON 



BovERi's Figures. 



//( A, the section pas.ses through a branchial cleft on the right side, and shows a 

 transverse section of the anterior limb of a nephridium {X) ; on the left, a 

 nephridium {X) is indicated showing its eomnmnication with the ccelome {B) 

 and with the atrial chamber (C). A, genital section of ccelome (an ovary is 

 indicated on the right side) ; I), section of the ccelome which extends down 

 the branchial bars ; F, ventral aorta. 



In. B, the section represents the pronephrio region on the left, and the meso- 

 nephric region on the right. A, rudiment of a mesonephrio tubule, the 

 blind end of which subsequently comes to open into the pi-o- (or meso-) 

 nephric duct (O) as indicated by the dotted lines on the riglit. B, nephro- 

 stome ; D, cojlome : F, subintestinal vein. 



//( both figures, E, lumen of gut ; O, aorta ; //, portion of commissural vessel 

 which comes into relation with the excretory system. 



ccelomic canals "). Each of these tubules comes into close relation 

 with a branchial blood-vessel, possesses a varied number of lateral 

 branches, and opens on the one hand into the coelome by several 

 ciliated funnels or nephrostomes, and on the other by a single 

 aperture into the atrial or peribranchial chamber (p. 275), which 



Kav 



