FEEDING HABITS OF FRESHWATER MUSSELS. 1 29 



their removal from the animal. This illustrates the fact that, 

 while the cilia generate considerable power, they accomplish it 

 upon a minimum of metabolism. 



The general character of the feeding habits of mussels has been 

 known for nearly a century. Fragmentary bits of information 

 on the various phases of the subject are to be found in the Mol- 

 luscan literature, particularly that concerning marine forms, to 

 whose study economic interest has added impetus. 



SCOPE AND NATURE OF INVESTIGATION. 



It has been the purpose of this investigation to determine for 

 fresh water forms, (i) what their food is, (2) how food material 

 reaches the alimentary tract. (For the most part there is great 

 similarity to the marine lamellibrancha in these two particulars, 

 but there are a few essential differences.) (3) Incidental to the 

 above a few observations concerning digestion. 



MATERIAL. 



In the work upon the nature of the food, lake-dwelling mussels 

 were used altogether. In the other studies river forms were also 

 used. Besides one or two unidentified species, the following were 



employed : 



Lampsilis luteolus Lamarck 



Lampsilis subrostratus Say 

 Quadrula rubiginosa Lea 

 Lampsilis alatus Say 

 Lampsilis rectus Lamarck 

 Unio gibbosus Barnes 

 Lampsilis ligamentinus Lamarck 

 Anodonta grandis Say 



Being by far the most numerous at Winona Lake, L. luteolus was 

 used for the greater part of the work. 



ANATOMY, AND PREVIOUS WORK ON THE FUNCTION OF THE 



CILIA. 



The mouth of the lamellibranch lies nearly as far as possible 

 from the external openings, just behind the anterior adductor 

 muscle. It is thus well protected from the entrance of harmful 



