26 Our Food Mollusks 



none of the bivalves are quite so good for food from 

 July to September; but the critical insight of the person 

 who declares an oyster stew or a clam-bake in August 

 to be failures from a gastronomical point of view, is 

 very much to be questioned. There is no very good 

 reason, except the difficulty of transporting and keeping 

 long neck clams, why all of our food mollusks should 

 not be marketed during the summer. 



The Nervous System. In a great many inverte- 

 brates, the central nervous system possesses one chief 

 ganglion, or pair of ganglia, situated in the anterior part 

 of the body. But in the bivalves there are three pairs 

 of large ganglia: one, the pair of cerebrals, in the region 

 of the mouth; a second, the pedals, in the base of the 

 foot ; and a third, the viscerals, close against the under 

 side of the posterior adductor muscle. 



The ganglia of the cerebral pair are often separated, 

 being placed on the right and left sides of the mouth. 

 These are connected by a strand or commissure of nerve 

 fibers crossing in front of the mouth. The two pedal 

 ganglia, connected with the cerebrals by a pair of com- 

 missures, are partially fused together. They supply the 

 muscles of the foot with nerves. The viscerals are the 

 largest, and are fused together into a single ganglion 

 from which nerves are given off to the gills and mantle. 

 A pair of commissures also unites visceral and cerebral 

 ganglia. 



Structurally this nervous system seems to be simple, 

 when compared with that of higher animals, and one is 

 apt to lose sight of the very complex functions that it 

 really performs. The responses of the attached and 

 greatly degenerated oyster seem to be few and simple. 

 Superficially regarded, its functions, except those per- 



