Food Relations of Fresh-Water Fishes. 489 



Catfishes alone seem purposely to eat leeclies, these occur- 

 ring in nine specimens of three different species of this family, 

 and also in one common sucker and in a single shovel fish. 

 This leech last mentioned and a small quantity of Plumatella 

 were the only Vermes eaten by the shovel fishes which I 

 examined. 



A planarian worm occurred in one small stone cat, while 

 rotifers were recognized in a common minnow, eight young 

 red-horse, six young chub suckers,^ five of the common sucker," 

 a single Carpiodes (young), and seven young buffalo. Polyzoa 

 were noted, in addition to the instances above mentioned, in 

 four common sunfishes, the croppie, and seven buffalo. 



SPONGES AND PROTOZOA. 



One of the fresh water sponges (Spongilla) had been eaten 

 in considerable quantities by two examples of the spotted cat 

 taken in September, but this element was not encountered 

 elsewhere in my studies. 



That the minutest and simplest of all the animal forms, 

 far too small for the eye of a fish to see without a microscope, 

 should have been recognized in the food of seventeen species of 

 fishes is, of course, to be explained only as an incident of the 

 feeding habit. It is possible, however, that these Protozoa, 

 where especially abundant, may be recognized in the mass by 

 the delicate sensory structures of the fish; and they seem in 

 most cases to have been taken with mud and slime rich in 

 organic substances, As most of them are extremely perishable, 

 and can scarcely leave a trace a few seconds after immersion in 

 the gastric juices of the fish, it is probable that they contribute 

 much more generally than our observations indicate to the food 

 of some fishes, especially to those which feed upon the bottom. 



Young suckers under six inches in length clearly take 

 them purposely, substituting them in great part for the Ento- 

 mostraca taken by other fishes of their size and age. 



I detected Protozoa in the food of several genera of 

 Cyprinidse, in the young of buffalo, the river carp, the chub 

 sucker, the red horse, the stone roller,' in the common sucker, 



^Erimyzon sucetta. ^Catostomus teres. ''Hypentelium. 



