THE MOLLUSCA 



99 



lae which separate above to form a canal opening outward 

 between the folds of the mantle at the posterior end of the 

 body. The surface of the gills is covered by fine cilia 

 which beat so as to cause a current of water to flow in 

 through small orifices between the filaments and into the 

 canals above the bases of the gills, and thence out through 



FIG. 82. Structure of the clam Anodonta, a. a, anterior adductor 

 muscle for closing the two valves of the shell; c.p.g, cerebropleural gang- 

 lion or brain; g, intestine coiled in the foot; g.L, gill; k, kidney; I. p., labial 

 palp; p.g., pedal ganglion; r, rectum; s.t. stomach; v, ventricle of heart 

 giving rise to arteries at each end; v.g., visceral ganglion just below the 

 posterior adductor muscle. (After Rankin.) 



the opening between the mantle lobes, called the exhalent 

 siphon. Water flows into the mantle cavity through the 

 inhalent siphon which is situated just below the exhalent 

 one. Place some colored fluid in a dish of water contain- 

 ing a clam, and you may see it drawn into the one opening 

 and expelled at the other. 



The lower part of the body projects in front into a 

 muscular organ, the/00/, which can be protruded between 



