78 The Food of the Smaller Fresh- Water Fishes. 



It is distinguished IVoin all other species by the great leiiirth of 

 the intestine, which is from six to nine times the length of the 

 body, and is spirally coiled about the air bladder. The gill-rakers 

 are iiumerovis, about twenty in number to each gill, but are very 

 short, scarcely projecting beyond the anterior margin of the arch. 

 They are evidently almost totally inefficient as a straining appa- 

 ratus. 



Of the great number of specimens available for dissection, only 

 nine were studied, since the contents of the intestines were found 

 so uniform in character that it was not deemed worth while to 

 multiply instances. These were from both extremes and also 

 from the center of the State, but were all taken in July, August 

 and September. The intestine was invariably filled from end to 

 end with a black and slimy matter, which, when examined vmder 

 the microscope, was found to consist almost wholly of fine mud. 

 When the intestine was emptied and the contents stirred up in 

 alcohol and repeatedly decanted so as to separate the coarser frag- 

 ments, the organic matter was easily distinguished. It made on 

 an average, only about one-fourth of the contents of the intestine, 

 the remainder consisting of the finest particles of sand and clay. 

 Not far from one-fifth of the whole amount was of vegetable ori- 

 gin, consisting chiefly of filamentous Algfe, mingled with a few 

 diatoms, but comprising occasionally minute fragments of other 

 kinds of vegetation also. The only animal objects noted were 

 occasional Chironomus larvpe and Difflugia. Sometimes the intesj 

 tine was wholly filled with almost pure mud, in which no organic 

 structures whatever could be detected. Date and locality seemed 

 to make no material difference in the food of this fish, which 

 should evidently be classed as limophagous. The ratios of ani- 

 mal to vegetable food were scarcely different from what one would 

 expect to find in the intestine of a fish which had the habit of 

 swallowing mud rich in organic matter, the greater ratios of vege- 

 tation being apparently due to the fact that plants are more abun- 

 dant in the water than animals. 



PiMEPHALES PBOMELAS, Raf. BlACK HeAD. 



This species is generally distributed tliroughout Central and 

 Northern Illinois, but is not very abundant. We have taken it 

 only in rivers and larger creeks, but have not found it south of 

 Jersey County. 



