Descriptive Zoology. 



and out of the upper siphon. The current is produced by 

 the vibration of the cilia which cover the outside of the gills 

 and the inner surface of the mantle. The entering current 

 passes forward around the body and gills. The palps are 

 also ciliated ; and between the two palps of each side the 

 minute particles are caught and passed on into the mouth, 



Blood tubes 



Blood currents 



FIG. 70. STRUCTURE OF CLAM'S GILL. 



whose upper lip is formed by a continuation of the two 

 outer palps meeting across the middle line, the two inner 

 palps similarly forming a lower lip. 



The Digestive System of the Clam. The mouth is just 

 back of the anterior adductor muscle. A short, wide 

 gullet extends upward and backward to the large spherical 



