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, 



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

 commissure anterior to the mouth; c, pedal commissure; d, pedal ganglia- 

 e, parieto-splanchnic commissures; /, parieto-splanchnic ganglia; g, branchial 

 nerves; ft, I, pallial nerves; i, siphonal nerves; k, anal nerves; m, nerves to 

 the anterior adductor muscle. 



is the pair of large collective branchial veins. The kidney, or " organ 

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





