FOOD AND FEEDING IN FRESH-WATER MUSSELS. 
453 
in Figure 26 (opposite p. 461). Apparently there was no selection of material, all 
sorts being ingested. 
A specimen of Lampsilis luteola was placed in a suspension of carmine. Par- 
ticles could be seen to pass across the inner face of the outer palp over the dark 
vertical streaks representing the furrows between the ridges. In their passage 
these particles were scattered across the upper half of the palp. At the same time 
other particles were passing down the vertical streaks to the lower edge of the 
palp and back to the posterior end and off. The mussel soon closed the valves 
and did not ingest until removed from the carmine. 
In all these cases the stream or rope of material mingled with mucus discarded 
from the lower posterior comer of the palp moved downward and backward along 
the lower part of the mantle chamber and was pushed out somewhat below the 
region of the inhalent siphon (fig. 6). 
Fig. 6. — Outline of mussel 12 mm. long, showing by arrows the course taken by material in the mantle chamber. AA, anterior 
adductor; PA, posterior adductor; F, foot; IS, inhalent siphon; ES, exhalent siphon; IG, inner gill; OG, outer gill; P, palp; 
E, mouth; S, stomach; I, intestine; E, rectum filled with material; M, mantle. 
MUSSELS FEEDING IN HEAVY SUSPENSIONS. 
A specimen of Lampsilis luteola about 3 mm. long was placed in a very heavy sus- 
pension of debris from the river bottom. Great quantities of material were drawn in 
around the foot, fell upon the gill (the inner, as yet) , and passed forward and between 
the palps. Heavy streams passed down the inner face of the outer palp, as described 
above, in fixed vertical rows and were thrown off in a very heavy mucus rope from 
the posterior corner. A very few particles were seen to pass along the upper part 
of the inner face of the palp to the mouth. Evidently the mussel could obtain at 
least a small amount of material even though the water were heavily loaded. 
A specimen of Lampsilis luteola about 3 mm. long was placed in a watch glass on 
a bottom of material from a creek bed, consisting of fine sand, debris, and small black 
particles (probably organic). The mussel crawled into this. The tentacles and siphons 
were extended then and plainly visible. A current passed in at the inhalent siphon, 
as in the adult. From 9.20 to 9.50 a. m. the mussel was all hidden but the siphons, 
and masses of debris were piled over these with a fine glass rod. This debris was 
87161°— 24f 2 
