132 GENERAL BIOLOGY 



Are any of the particles carried far enough forward to reach 

 the mouth? In the clam it is by ciliary movements that 

 small organic particles are carried to the mouth, and the 

 entire food is composed of these particles. 



4. Heart Beat. In a specimen with one shell removed 

 observe carefully the region of the body dorsal to the gills 

 and in front of the posterior adductor muscle. This is the 

 position of the heart and its pulsations may be seen through 

 the delicate walls of the mantle. If care is used one may 

 remove the mantle and pericardial walls and expose the 

 heart itself. When the heart is exposed the pulsations of 

 auricle and ventricle may be easily observed. 



