8o Laboratory Guide in Zoology 



anterior to the foot, and below the anterior adductor 

 muscle, search for the mouth, a small opening, some- 

 times difficult to find. Force a bristle into this up to 

 the stomach coils. 



XII. — Attached to the walls of the body, and on each side 

 of the mouth find a pair of soft triangular flaps, the 

 labial palpi. 



XIII. — Gently detach the body of the clam from the shell 

 close under the hinge. Where the two mantle lobes 

 unite to form the dorsal body wall, the latter is so thin 

 that you may look through it into the body cavity and 

 see the straight intestine passing from end to end. Try 

 to see the pulsing, colorless, ventricle of the heart, 

 through which the intestine passes, though the cavitjes 

 of the two have no connection. With pincers apd 

 sharp-pointed scissors carefully lift and cut the body 

 wall so that the boundaries of the body cavity and its 

 organs may be more easily seen. 



XIV. — Trace the intestine forward toward the mouth. 

 Examine the dark brown mass surrounding the coils of 

 the stomach. This is the liver (very evident in stews 

 of the edible clam). As is the usual function of that 

 organ, it secretes a digestive fluid that passes into the 

 interior of the alimentary canal. 



XV. — Trace the intestine backward, and notice that it 

 ends in a space into which the dorsal opening of the 

 siphon opens. This space is called the cloacal chamber. 



XVI. — Determine the course taken by the water that 

 passes in at the ventral opening. Notice that it bathes 

 the gills, the lower part of the body wall and foot, and 

 the inner side of the mantle lobes ; then it passes for- 

 ward to the labial palpi and the mouth. The cilia which 

 cover the labial palpi keep up a constant vibratory 



