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BULLETIN OF THE BUREAU OF FISHERIES. 
point below the incurrent siphons in a more or less continuous stream during feed- 
ing. 2 
Baker (1916) lists as feeding on detritus and plankton Lampsilis radiata, L. 
'borealis, L. luteola, L. iris, Anodonta cataracta, A. implicata, A. marginata, A. 
grandis footiana, Strophitus undulatus and Margaritana margaritifera. 
Nelson (1918) found in fresh-water mussels that the esophagus was lined with 
cilia, which carry the ingested particles to the stomach. He also described the 
large tufts of cilia on certain cells lining the stomach, which cilia cause to rotate 
the crystalline style, the anterior end of which projects from the intestine into the 
stomach. Nelson showed that the style in lamellibranchs possesses at least four 
functions: (1) Separating foreign particles from the food in the intestine, (2) 
serving as a substitute for peristalsis, (3) restoring, in some species, to the stomach 
undigested food particles that have started down the intestine, (4) bearing enzyms. 
His conclusions relative to the possibilities of a lamellibranch feeding in heavily 
turbid waters are given below. 
Cobb (1918) found that both the attached and the detached palp responded 
to mechanical, chemical, electrical, thermal, and photic stimuli by curling outward 
and upward at its free (posterior) tip. Such a reaction would cause the ridges, 
which would be on the convex side of the curled palp, to be pulled farther apart, 
allowing the cilia in the grooves to be more exposed and more material to be carried 
down to the lower edge of the palp. This curling reaction was observed by the 
present authors in juvenile mussels actually feeding, as will be described later, and 
fits in well with Kellogg’s statements relative to an elongation of the palp to expose 
the cilia in the grooves; the curling would make the convex side longer and the 
ridges farther apart. 
Evermann and Clark (1920) published extensive lists of material found in the 
alimentary tract of the fresh-water mussel. These include a wide variety of diatoms 
and other algae, Protozoa, and organic and inorganic debris. 
Coker, Shira, Clark, and Howard (1921) concluded that there is practically 
no discrimination in the kind of material ingested in nature, listed a variety of 
plant and animal forms, laid stress on the quantity of detritus taken, found con- 
siderable mud in certain adult mussels, and stated that in 60 juveniles ranging 
from 5 to 21 mm. long, the contents of the alimentary canal consisted of about 92 
per cent “organic remains (principally vegetable matter),” 3 per cent “inorganic 
remains (silt, etc.),” and about 5 per cent unicellular green algse and diatoms. 
Certain feeding experiments were performed, which tended to show that detritus 
formed the main bulk of the food in nature, although considerable quantities of 
plant and animal forms were taken. Substances such as fish meat, tadpole tails 
(macerated), animal fat, fish blood, and fresh vegetable were not taken as readily, 
or scarcely at all in some cases. Olive oil in the form of an emulsion was ingested 
and digested by certain of the mussels. 
Bush (1922) studied the histology of the groove in the ventral edge of the inner 
gill and showed that it is lined with ciliated cells by means of which the material 
that has passed down the gill is carried forward to the palps (fig. 3) . 
2 This expulsion has no relation to the occasional ejection of material from the mantle chamber by a spasmodic closing of 
the valves, such as is often observed. — Authors. 
