allowed to settle in the water past the margins of the shell of an 

 extended individual will show that such variations in the cur- 

 rents do occur. 



This current of water not only supplies the means of respira- 

 tion, allowing the blood that is passing through the gills to 

 become charged with oxygen and to rid itself of carbon dioxide, 

 but it serves to supply the animals with food. 



The food for the most part consists of microscopic plants 

 which are strained out of the water that passes through the 

 inhalent ostia. These are passed along the surfaces of the gills 

 by the cilia that cover the surfaces of the filaments, to their free 

 margins and along the margins to the anterior ends of the gills. 

 Here they are passed between the labial palps which inclose the 

 anterior ends of the gills, and so on into the mouth. 



Attention has not been given to the action of the feeding cilia 

 in this form, but Kellogg (15) and Stenta (31) have found that 

 the action is apparently under control in many forms, so food 

 that is passed over the surface of the gills may be carried to the 

 palps or may be passed onto definite tracts of cilia on the mantle 

 that carry it away and finally eject it from the mantle chamber. 

 It would thus seem that while the cilia on a gill are active, food 

 is being strained out but that the animal may or may not eat 

 the food gathered. 



The ability to accept or to reject solid material that is brought 

 to the gills in the current of water that is formed by the cilia- on 

 the gills is indicated by examining the stomach contents, as well 

 as by the observations made by Kellogg and Stenta. The study 

 of the food that is in the stomach shows that there has actually 

 been selection of materials and that the ability to reject is not 

 simply to allow the animal to continue respiration without feed- 

 ing, for there are many forms of diatoms that are abundant in 

 the water in which the animal lives that are not present in its 

 stomach. The observations of Grave (8) on the food of the 

 oyster indicate how great this selection may be and no one who 

 has given any attention to the stomach contents of lamellibranchs 

 will doubt that food selection is common among members of the 

 group. No observations have been made on the speed with 

 which food is gathered by scallops but as the method of feeding 

 is so similar for most lamellibranchs the observations made by 



29 



