212 WILLIAM RAY ALLEN. 



brought into captivity defecation usually continues to occur even 

 after several hours, and indicates that feeding has at no time been 

 long suspended. The normal position of the palps, gills, and 

 mantle with respect to each other is favorable to ingestion. The 

 structure of the mussel is such that it requires a greater effort 

 to refrain from feeding than to continue feeding. The ciliary 

 apparatus is in constant activity, regardless of the presence or 

 absence of food. The gills are at all times siphoning water. 

 Particles suspended in the water are at all times being sifted out 

 and caught upon the mucous secretions of the gills. The gills 

 have no way of rejecting such collections. They are always 

 passed on by the fixed ciliary tracts of the gills to a given point 

 on the lower margin of the inner gill which hangs between the 

 labial palps. Without an adverse stimulus and an avoiding move- 

 ment of the palps the collections pass on to their apposed surfaces. 

 Thence it is but a short distance to the mouth. 



If, despite the structure of the mechanism of ingestion, one 

 might still doubt that feeding is a constant process, he is forced to 

 grant that feeding is speedily resumed by mussels artificially 

 starved. Those starved a sufficient length of time to get rid of 

 the crystalline style, when placed again in lake or stream, begin 

 the renewal of the style within fifteen to thirty minutes. 



(a) The Feeding Posture. 



To what extent feeding is conditioned by the position of the 

 mantle, palps, and gills the following experiment will show : 



Some LainpsUls and Anodonta were starved several days to 

 insure the disappearance of the crystalline styles. The renewal 

 of these organs was then taken as an index of the feeding activi- 

 ties. Various individuals were placed in the lake, in lake water, 

 and in Pocahontas creek. Some were partially inserted in sand 

 in the normal posture, others with the siphons turned upward, 

 others laid upon the right or left side, and still others upon the 

 hinge and having the gape of the shell uppermost. 



At intervals some from each situation were examined. The 

 styles were found to be reformed in all of them at about the same 

 rate. The position of the ciliated parts, with relation to one 



