104 



THE FRESHWATER MUSSEL. 



5 The course of the circulation. 



The ventricle receives arterial blood from the 

 auricles, and drives it through the arteries all over 

 the body. The blood from the foot and viscera is 



K R U GO U0 



PR \ \ i r P \ 



SC LM i 



Fio. 29. Anodonta cygnea. Diagrammatic view from the right side. 

 The right valve of the shell, the right mantle-lobe, the right gills, 

 and the right auricle have been removed. The alimentary canal 

 has been laid open from the right side as far as the point where it 

 enters tho pericardial cavity. The pericardial cavity, the ventricle, 

 and the right kidney and ureter have been laid open from the right 

 side. The longer arrow passes from the pericardial cavity through 

 (he right reno-pericardial aperture into the right kidney. The 

 shorter arrow passes through the external aperture of the right 

 ureter, (a. m. m.) 



A, margin of the loft valve of the shell in which the animal is lying. AA, 

 anterior adductor muscle. AN, anus. B, ligament of the shell. BD, bile-duct. 

 BD', openings of bile-duct into stomach, c, cloacal cavity. D, septum 

 between tho cloacal and branchial cavities. E, tentacles bordering inhalant 

 aperture, f, foot. G, line of fusion of inner lamellae of right and left inner 

 gill*. GO, genital aperture. H, anterior aorta. I, intestine. K, kidney. 

 L, liver. LG, inner gill of left side. LM, left mantle-lobe. M, mouth. N, 

 posterior aorta, o, oesophagus, pa, posterior adductor muscle. PC, peri- 

 cardial cavity. PR, right posterior retractor muscle. R, rectum. RG, genital 

 gland ovary or testis, rm, line of attachment of right lobe of mantle. RP, 

 right rono-poricardial aperture. s, stomach. SC, median supra-branchial 

 canal, lying above the inner gills. T, typhlosole. U , right ureter. UO, external 

 opening of right ureter, v', cavity of ventricle. 



