FOOD AND FEEDING IN FRESH-WATER MUSSELS. 
449 
made to learn what happened in case the mussel were upon a substratum in which 
it might partly bury itself, leaving exposed the posterior end where the siphons 
later develop. This latter position is, of course, that assumed by the older stages 
after the byssus has disappeared, and possibly by the very small ones before the 
development of the byssus. The byssus does not appear until the mussel is over 
1 mm. long. 
Accordingly, a specimen of Lampsilis luteola about 1 mm . in length was placed 
on a substratum of sand grains about the size of the mussel, into which sand grains 
it at once crawled. These were then moved with a needle, so that a portion of the 
anterior end of the mussel was visible through the chinks between them. Fine 
debris was gently dropped from a pipette upon the sand grains. Particles of the 
debris could be seen to be sucked down between the grains and into the anterior 
end of the mantel chamber of the mussel. It would appear that in a mussel of this 
Tig. 2. — Side view of mussel about 2 mm. long. A A, anterior adductor; PA, posterior adductor; F, foot; G, gills; IP, inner palp; 
OP, outer palp; L, liver; M, mantle; Mo, mouth; St, stomach; Int, intestine. (Adapted from Herbers.) 
size, with no siphons, the currents enter all along from the midventral side to 
the anterior end. 
Several specimens of Lampsilis luteola were observed. A current of particles 
consisting of fine debris passed in around the foot. Part of these were carried for- 
ward to the mouth and part passed off the palps, down along the inside of the mantle 
and back to a point at the posterior end below the place where the inhalent siphon 
later develops. Here they passed out of the mantle cavity, as stated by Kellogg. 
No cilia could be seen on the edges of the mantles in the siphonal regions, although 
cilia were visible elsewhere along the edges of the mantles. 
A specimen of Lampsilis luteola was placed in a heavy culture of Euglenas meas- 
uring about 60 by 18 micra when elongated. Some were rolled up in an approxi- 
mate spherical shape and measured about 25 micra in diameter. The mussel opened 
at intervals and took in some Euglenas. In several instances a particular Euglena 
was observed throughout its entire journey from the outside to the stomach. It 
