27^ 



SWAN MUSSELS. PHYLUM MOLLUSCA 



EXCRETORY ORGANS AND GONADS 



The kidneys or organs of Bojanus (Fig. 207) are two in number 

 and lie side by side below the pericardium. Each is a wide tube, 

 doubled on itself, with one Hmb above the other, and the two ends 

 close together in front. The lower limb is glandular and opens 



Fig. 206. 



-A semi-diagrammatic drawing of a transverse section of the swan 

 mussel in the region of the hinder part of the foot. 



au.. Auricle ; B, glandular limb of kidney ; B', non-glandular limb of the same ; com., commissure, 

 between cerebral and parietosplanchnic ganglia ; ep.sp.. epibranchial spaces ; /., foot ; gen., gonad ; 

 i.g., inner gill ; i.l.j., interlamellar junction ; il.sp., interlamellar spaces ; int., intestine ; tn.f., 

 muscular part of the foot ; ml., mantle lobe ; e.g., outer gill ; pm., pericardial cavity ; rm. rectum; 

 v., ventricle; v.c, vena cava. 



upwards into the front end of the pericardial cavity by a crescentic 

 renopericardial opening in the floor. The upper limb has thin 

 walls and opens downwards into the space close to the gills 

 shortly before the point at which the inner lamella of the inner 

 gill becomes free. The organ is a coelomoduct and excretes some 

 nitrogenous material. Coelomic fluid is drawn by ciHary action 

 through the renopericardial opening into the kidney and is 

 discharged as urine by contractions of the organ. The urine is 



