FOOD AND FEEDING IN FRESH-WATER MUSSELS. 
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colonies of green algae, the desmid Staurastrum, Scenedesmus, and the diatom 
Cyclotella, besides much debris. 
Examination was made of the contents of portions of the alimentary canal of 
mussels varying in size from 9 to 15 mm. long, the smaller ones being dissected 
under the binocular microscope. Some were from the rearing trough, others from 
the Mississippi River. A list of various organisms and material found in them 
follows. Greenish-brown masses consisting apparently of mucus, organic debris, 
and the following entire or fragmentary recognizable forms: Trachelomonas, two 
or three species, numerous ones living; tests of the rotifer Keratella cochlear is; 
Chlamydomonas, some living; Monas sp., one living; Phacus pleuronectes; P. longi- 
caudus; Peridinium tdbulatum; Euglena acus ; E. spirogyra; E. deses; encysted 
Euglenas; Kirchneriella sp.; Pediastrum duplex; Tribonema sp.; Scenedesmus quad- 
ricauda; S. acuminatus; S. denticulatus; S. arcuatus; S. dimorphus; S. brasiliensis; 
S. abundans; S. bijuga; S. arcuatus platydisca; Coelastrum sphaericum; C. micro- 
porum; Crucigenia irregularis; C. quadrata; Chroococcus minutus; Tetraedron cauda- 
tum or pentaedricum; Tetrastrum staurogeniseforme; Pandorina morum; Microcystis 
incerta; Aphanocapsa pulchra; Merismopedia punctata; M. tenuissima; Platydorina 
caudata; Staurastrum sp.; Pediastrum duplex; P. tetras; P. simplex duodenarium; 
Pandorina sp.; Selenastrum westii; Platydorina sp.; Microcystis incerta; Staurastrum 
sp.; Pleodorina calif ornica; Oocystis; Dinobryon setularia; Tetraedron sp.; Volvox; 
numerous green cells of broken-down colonial algae forms; many species of diatoms, 
some filamentous; empty tests of diatoms, and cells broken from filaments. Some 
specimens contained great numbers of empty loricas of Dinobryon, one fragment 
being made of over 20 united zooids. 
ADULT MUSSELS. 
The alimentary tracts of some dozen mussels were examined either immedi- 
ately upon being taken from their natural environment or after having had the 
adductor muscles cut and being placed in formaldehyde to stop digestion and 
preserve the intestinal contents. Some of these mussels were taken from the 
Mississippi River, some from Lake Okoboji, and some from the Little Sioux River 
(Iowa). The following is a list of the kinds of material found in the alimentary 
canal : 
Greenish mass made up of mucus in which were mingled Difilugia tests; Diatoms, 
various species; Volvox; Pleodorina, whole and fragments; algae, whole and frag- 
ments; sand grains, one 752 by 400 micra, others 44 by 28 micra, and smaller; 
Microcystis; fragment, 960 micra long, of cellulose wall of plant; lorica of a clado- 
ceran 720 micra long; loricas of rotifers, probably Anuraea; a flagellate, apparently 
Lagerheimia; Scenedesmus; Pediastrum; fragments of filamentous algae; Staurastrum 
brevispinum; Coelastrum sphaericum; Euglenas, normal and encysted — some living 
and active — Euglena viridis, E. deses; E. acus; fragment 70 micra long of a small 
crustacean. Debris, organic and inorganic, and sand grains were found in every 
specimen examined. 
Allen says, "As stated by Zacharias, Petersen, the writer [Allen], Baker, and 
others, considerable quantities of inorganic and organic debris are carried into the 
