POLYODOX — PADDLE-FISHES 19 



monly creeping over the mud or swimming near the bottom, it 

 is likely that this fish is usually a bottom feeder. One of our 

 specimens contained nothing but insect food, the ephemerid 

 larvae above mentioned amounting to 85 per cent, of 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 alimentarj^ structures. 

 The very remarkable straining apparatus borne by the gills, 

 the immense mouth-opening, and the equally large gill-slits, pro- 

 vide 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 apparatus 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 con- 

 sequently on the stores of insect and crustacean life most com- 

 monly reserved for young or half -grown fishes. It thus be- 

 comes 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. Kofoid learned that "in swimming the mouth is held 

 wide open, without the rhythmical respiratory movements com- 

 mon 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 perceives plankton or ground fish 

 added to the water of the tank, and, when feeding, circles re- 

 peatedly over the same path, at times dragging 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 au- 

 thentically reported. Females full of nearly ripe roe have been 

 seen by different observers in this latitude in the latter part of 



