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, 
commissure anterior to the mouth; c, pedal commissure; d, pedal ganj^lia- 
e, parieto-splanchnic commissures; /, parieto-splanchnic gangha; branchial 
nerves; h, I, pallial nerves; i, siphonal nerves; fc, 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) lying below 
