68 



ZOOLOGY. 



the so-called "aortic bulb." The arterial system is quite compli- 

 cated, as is the system of venous sinuses, which can be best studied 

 in carefully injected specimens. At the base of the gills, however, 



Fig. 76.— Nervous system of the clam, natural size, a, oesophageal ganglion; 6, 

 coxnmisHure anterior to the mouth; c, pedal oouimissure; d, pedal ganglia: 

 e. parietosplanchnic commissures; /, parieto-splanchnic gangha; g, branchial 

 nerves; K /, pallial nerves; i, siphonal nerves; fc, anal nerves; m, nerves to 

 the anterior adductor muscle. 



is tliepairof largo collective Ijranrhial veins. Tlie kidney, or "organ 

 of Bojauus," is a large dusky glandular mass (Fig. 75, 4) lying below 



