12 ' NEW YORK STATE MUSEUM 



lengthened or shortened, and, if their inner faces touch the edges 

 of the gills, any material which is being brought to this region is 

 transferred onto the ridges of the palp. This is accomplished by 

 strong cilia which are developed on the ridges. These same cilia 

 carry the foreign matter on across the ridges, and finally force it 

 into the mouth [arrow on /?/>]. 



This, in brief, is the method by which clams and oysters and 

 other lamellibranchs collect and ingest their food. The process, 

 till very recently, has not been closely studied, but this auto- 

 matic feeding process has been known in a general way for a 

 long time. It has sometimes been said that, if a lamellibranch 

 is to prevent suspended mud from being collected by the 

 gills, it must close its shell, thus entirely preventing all ingress 

 of water into the body. It has been found that these creatures 

 have no more control over the activities of the cilia which have 

 been described than a man has over the cilia in his trachea. As 

 long as the animals live, the cilia continue to lash in the same 

 definite directions, though their activities soon become lessened 

 after the shell is removed. 



But I have found that the animal can prevent food or particles 

 of dirt from being taken to the mouth while the stream of water 

 is yet flowing. It seems never to have been suspected that 

 complicated mechanisms existed, by means of which collected 

 particles could at once be discharged from the body. They are 

 present, however, probably in all lamellibranchs, differing some- 

 what in different forms, and I shall describe the comparatively 

 simple one which is found in Venus. 



If the mantle and gills are removed from one side of the body, 

 so as to expose the visceral mass and the foot, and the creature is 

 put into a dish of sea water, grains of carmine, which are allowed 

 to settle on the surface of the visceral mass, at once indicate the 

 presence of a ciliation there, as well as on palps and gills. These 

 experiments require care and patience, but they show with great 

 certainty that the most definite cilia currents exist in this region. 

 These are indicated by the arrows placed on the visceral mass in 

 figure 2. It will be seen that all the currents converge at a definite 

 point, X, just above the line of the base of the muscular foot on the 



