FOOD AND FEEDING IN FRESH-WATER MUSSELS. 
457 
the body of mussels of this size is too opaque to allow sufficient light to pass through. 
At frequent intervals rolls or masses of mucus could be seen to move downward 
across the palp, bringing entangled filaments along. These masses dropped off the 
ventral edge of the palp into the mantle cavity and were carried back along the 
ventral side of this and thrown out just below the inhalent siphon, taking the 
filaments with them. 
Some of the filaments that entered the mantle chamber were carried well up 
to the dorsal side near the umbo and lodged there for a time, apparently out of 
reach of cilia. Eventually, however, they would be moved downward to the palp. 
Some filaments were seen to have been carried to a point entirely forward of the 
palps, dorsal to the anterior part of the foot. Their precise course in reaching this 
region was not ascertained. These were later carried downward and along the 
ventral side of the mantle chamber and out. It should be emphasized that in this 
and the preceding observation the mucus masses were ejected from between the 
gaping valves below the inhalent siphon fairly steadily, being forced out by the 
action of cilia located on the inner surface of the mantle, not by spasmodic clos- 
ings of the valves. The latter remained motionless during the process. 
STUDY OF SECTIONS OF THE PALPS. 
ADULT MUSSELS. 
Prof. H. Walton Clark, of the Fairport staff, removed several specimens of 
Anodonta imbecillis 10 to 12 mm. long from the river and placed them at 
once in Bourn's fixative. This killed them instantly, and in a few hours the shells 
were decalcified by the acetic acid in the fixative. The mussels were then run 
through the alcohols and cleared in cedar oil. Several specimens so prepared were 
kindly placed at the disposal of the authors by Mr. Clark. One valve and mantle 
of these were dissected away with needles under a binocular microscope. The 
intestine and in some cases the stomach contained ingested material; also in 
many instances masses of material could be seen upon the palps, some in the 
grooves, some along the upper part, some forward near the mouth, and sometimes 
a mass in the esophagus. 
The region of the crystalline style was clear and colorless except for a little 
material along the sides of the style, this serving to mark it off and render it more 
easily discernible. In some cases the head of the style was visible in the stomach. 
Some of these mussels were lightly stained with borax carmine and photomicro- 
graphs were taken, two of which are shown in Figures 22 and 23 (opp. p. 459) . One 
or the other of these figures shows the points just enumerated, and Figure 23 shows 
also a mass of debris just leaving the lower posterior corner of the palp. 
Frontal sections, which would cut the ridges and grooves transversely, show 
that vertical ciliated ridges and grooves occur on the inner faces of the palps of 
mussels from at least the length of 1 mm. upward (figs. 9 to 16, inclusive). 
Figure 14 is that of a portion of the palp of an adult Lampsilis luteola sectioned 
transversely to the ridges and grooves and shows the ciliation quite clearly. Data 
were kept so that the anterior and posterior ends of the palps could he recognized 
in the sections. In this figure the free edges of the ridges lean toward the anterior 
