REPORT OF COMMISSIONER OF FI6H AND FISHERIES. XXXVIT 



more simple aud ecoiiomical. The system may also prove to be capable 

 of practical application to aquaria, doing away with the necessity of 

 new-water circulation. The idea is to atomize the water in a vessel 

 under an inverted cylinder so as to return the aerated water without 

 evaporation, and to cause the waste air used in atomizing to pass 

 through the water of the vessel, thereby imparting to it additional 

 oxygen. The water which is atomized is drawn from the bottom of the 

 vessel, thus inducing circulation. In experiments made in 1889 it was 

 found that one atomizer would aerate 100 gallons in twenty-four hours 

 under 10 pounds air pressure. This method is free from the objection 

 found in the use of nozzle jets, whicli cover the bodies of the fish with 

 air bubbles. It can also, probably, be made applicable in the move- 

 ment of fry, which can not be done with the first method. 



Fish Ponds, WAsniNiiTox, D. C. (R. Hesskl, Superintendent). 



In addition to the propagation of the carps, tench, golden ide, and 

 goldfish, and the rearing of the shad, the culture of the black bass and 

 the spotted cattisli was also undertaken. The distribution of the prod- 

 uct of the station was made through Central Station, the work having 

 been commenced in November. 



Carp. — The fisb distributed in the fall of 1891 were reared in two 

 large and two small ponds, the product being: 



Leather carp 94, 000 



Blue leather carp 2, 630 



Scale carp 54, 300 



Blue scale carp 6, 560 



Total 157,490 



The arrangements necessary for the spawning of this and the other 

 si)ecies of fish propagated at this station were changed from previous 

 years owing to the attention given to the black bass and spotted cat- 

 fish, and the pond space formerly allotted to the carp was reduced. 

 The stock of large breeding fish was placed in the ponds about the 

 middle of May, 1892, and a few days after they gave the first indications 

 of spawning, which quickly followed. The eggs developed rapidly 

 and three days after their appearance the dark spots were plainly 

 visible, and on the fourth and fifth days the young a^jpeared in consid- 

 erable numbers. Large quantities of eggs secured from the other breed- 

 ing fish were also placed in the ponds in proper beds, and they also 

 rapidly developed. The growth of the young was not so rapid as in the 

 preceding season. The cause of this is ascribed to the cool nights of 

 May, which lowered the temperature of the water and thereby retarded 

 their growth. 



Tench. — The product of this species for the summer of 1891 was 

 9,G00, the fish being reared in four small ponds. In 1892 they were 

 confined to two ])()nds. They commenced to spawn the early i>art of 

 June, sparingly in one, but abundantly in the other, with a fair prospecj; 



