go BULLETIN OF THE BUREAU OF FISHERIES. 



the utmost care had to be employed so as not to feed particles of food exceeding a 

 certain size. A neglect of this caution invariably caused violent expulsion of the 

 whole dose of food, no matter what it was. 



Thread Alg^. — These were accepted by all four species, but only in limited 

 quantities by the mucket, Lampsilis ligamentina. An examination of feces confirmed 

 the previous obser\^ations that green algse are only very incompletely digested. 



Palmellales. — These soft, slimy, green algae gave no other result save that they 

 seemed somewhat better digested by the blue-point mussel. 



Detritus. — -This was artificially prepared by immersing the leaves and soft stalks 

 of plants that are generally found near the water in some water for a few days until 

 nitrogenization had set in. They were then macerated with mortar and pestle and the 

 resulting pulp strained through bolting cloth. All mussels took this artificial detritus 

 readily, and the feces showed the characteristic features of digested detritus. 



Fresh Vegetable Material. — This was not so readily taken. 



Vegetable Fat. — Olive oil in the form of an emulsion was accepted by the Lake 

 Pepin mucket and the river mucket. It was evidently thoroughly absorbed, as no 

 traces could be found after digestion. The blue-point and the spike were not tried with 

 this material. 



EXPERIMENTS IN FEEDING ANIMAL MATTER." 



Fish Meat (heart of the wall-eyed pike, Stizostedion vitreum). — Two out of three 

 examples of the Lake Pepin mucket accepted this material readily, the third less so. 

 The control mussels vacillated, occasionally taking very small quantities. The other 

 three species evinced strong repulsion, expelling any of the substance taken in in from 

 I to 15 seconds. Abnormal reddish feces. 



Tails of Tadpoles (macerated). — These were refused or quickly expelled by 

 the river mucket and the Lake Pepin mucket. The other mussels were not tried with 

 this material. 



Blood of Pickerel. — ^This was refused by all species, even when given in a state 

 of high dilution. 



Animal Fat. — This was an emulsion of fat obtained from the sheepshead fish, 

 Aplodinotus grunniens. Extremely small doses at long intervals were taken and evi- 

 dently digested. 



In all these cases the food matenal was generally readily taken (from i to 1 5 seconds) 

 into the siphon. After a varying period of time (a few seconds), the length of time 

 necessary for the substance fed to affect the taste organs, disagreeable food was always 

 expelled again. 



The experiments do not point to any undoubted conclusion regarding animal food, 

 except that they seem to establish the fact that vegetable food is preferred to the animal 

 substances employed. Probably, under normal conditions, small quantities of the 

 latter are taken in with other substances, but it is hardly believed that it ever plays 

 a large r61e. 



GENERAL observations. 



Throughout the experiments it was noticed that the Lake Pepin mucket, Lamp- 

 silis luieola, was not so exact in its requirements as the river mucket, Lampsilis liga- 

 mentina. The latter was indeed the most delicate feeder of the four species, and the 



t Allen (1914, p. 13S) fed mussels upon living Paramecia with apparent success. 



