446 
BULLETIN OF THE BUREAU OF FISHERIES. 
suspended matter per liter,” thus calling into question Kellogg’s conclusions in this 
connection. 
Martin (1923) made examinations of the stomach contents of oysters under 
natural conditions and conducted feeding experiments. He found that they 
ingested animal and plant forms and artificially ground algal forms. In some cases 
the particles of ground marsh grass ( Spartina glabra ) were not ingested but found 
imbedded in mucus at the bottoms of the mantles, which circumstance was taken 
to indicate that this material had been rejected. 
MATERIALS AND METHODS. 
The following species of mussels were used in the investigations: Lampsilis 
gracilis, L. Isevissima, L. anodontoides , L. fallaciosa, L. ventricosa, L. luteola, Obovaria 
ellipsis, Anodonta grandis, A. corpulenta, A. imhecUlis, Quadrula pustulosa, Q. 
pustulata, Q. undata, Q. plicata, Obliguaria rejlexa, Plagiola donaciformis, and 
Sphserium sp. 
The species Lampsilis luteola is abundant in Lake Okoboji and furnished the 
basis for much of the work done there. Juveniles of this species, available in 
quantities from the propagation experiments as stated above, furnished the basis 
for a large share of the direct observations made upon the feeding reactions in 
juvenile mussels. 
Owing to the transparency of the valves of the juveniles it was possible to 
observe directly under the binocular microscope, when light from a 75-watt electric 
light was reflected up through the mussel, the ciliary action of gills, mantle, and 
palps, and the ingestion of food. Feeding experiments were also made with both 
juvenile and adult mussels and the contents of the alimentary canal examined 
both by means of paraffin sectioning and by dissection. Examination was made 
of the contents of the stomachs and intestines of mussels taken directly from troughs 
in which the propagation experiments were being conducted, and also of specimens 
taken from Lake Okoboji, the Little Sioux River near Lake Okoboji, and the 
Mississippi River at Fairport. 
The anatomy of the palps and gills of juvenile and adult mussels was studied 
with reference to the feeding process, largely by means of sections stained with 
hematoxylin and eosin. 
INGESTION. 
To summarize the general process of ingestion, the action of cilia on the gills 
and in the superbranchial chamber causes a current of water to enter the inhalent 
siphon, pass through the gills into the superbranchial chamber, and out the exhalent 
siphon. Cilia upon the gill filaments intercept the particles (animals, plants, de- 
bris, and the like) contained in the stream of water. These are entangled in mucus 
secreted by certain cells of the surface of the gills, and through the concerted action 
of the cilia the masses of mucus, together with the contained particles, are carried 
forward on the gills and deposited upon the labial palps. Cilia on these carry the 
mucus and the particles either to the mouth or to the ventral edge of the palps, 
where they fall into the mantle chamber. In the latter case the material drops to 
the edge of the mantle chamber and is carried backward by the cilia near the ven- 
