POLYODON PADDLE-FISHES 19 



it. In another, 30 per cent, of the food was algae belonging to the 

 genus Nostoc ; in still another, Entomostraca made 80 per cent, of the 

 food, and in a second specimen, 95 per cent. 



An explanation of the peculiar feeding habits of this species is to 

 be found in its no less remarkable alimentary structures. The very 

 remarkable straining apparatus borne by the gills, the immense 

 mouth-opening, and the equally large gill-slits, provide for the 

 rapid passage of enormous quantities of water through the gill- 

 chamber, and for the thorough straining out of all contents available 

 for food. The absence of any raptatorial teeth or crushing appara- 

 tus in its large and feeble jaws or in its throat makes it impossible 

 for the paddle-fish to capture other fishes or to break the shells of 

 mollusks, and it is dependent consequently on the stores of insect 

 and crustacean life most commonly reserved for young or half- 

 grown fishes. It thus becomes a rival, for food, of all the other 

 species in our waters, living continuously upon objects which all of 

 them must have for at least a part of their lives. 



By observing its feeding operations while in confinement, Dr. C. 

 A. Kofoidlearned that "in swimming the mouth is held wide open, 

 without the rhythmical respiratory movements common in most 

 • fishes, though it is occasionally closed energetically. The plankton 

 is thus strained from the water by the long gill-rakers, and Polyodon 

 is a living plankton-net. The fish was never observed to use the bill 

 to stir up the bottom, or in any mechanical way. It quickly per- 

 ceives plankton or ground fish added to the water of the tank, and, 

 when feeding, circles repeatedly over the same path, at times drag- 

 ging the lower fins upon the bottom. ' ' 



In swimming slowly by the use of its caudal fin, its head and 

 paddle are thrown alternately to the right and left, the tip of the 

 paddle thus covering a considerable space on each side of the line 

 along which it is swimming. 



Little is known of the breeding habits of the paddle-fish. The 

 young have been much sought by zoologists, but up to the present 

 time none under 6 or 8 inches in length have been authentically 

 reported. Females full of nearly ripe roe have been seen by different 

 observers in this latitude in the latter part of May, but the attempt 

 to find their spawning beds has thus far failed. Dr. Kofoid reported 

 a 30-lb female taken moving down stream at Meredosia May 5, 1899, 

 which had evidently completed spawning, the large ovary being 

 flabby and spent. On the other hand, a male weighing 25 lb, taken 

 in Meredosia Bay, had the testes large and full of milt. It is a 



