216 Phylum Art hr op oda 



gram each of sodium chloride and calcium sulfate per liter of water were 

 added. This solution was stocked with Daphnia. More infusion was 

 added later as needed. 



Experiments have shown that sunlight is important in the propagation 

 of Daphnia and many methods which are successful in strong sunlight 

 will not work when sunlight is completely absent. 



The second method was found best and most desirable for indoor 

 propagation since sunlight is not necessary. It depends essentially on a 

 combination of bran infusion and liver. Although the latter may be used 

 alone, experiments indicate that a combination of the two may be more 

 desirable than either alone. 



Ten grams of wheat bran were added to 1500 cc. of water and fer- 

 mented a week, as before. The supernatant fluid was poured off and dis- 

 carded; only the bran residue was used. This was then added to a shal- 

 low tank of about 100 liters' capacity, salt and calcium sulfate being 

 added as before. The liver was heated as rapidly as possible until the 

 proteins were coagulated. It was then cut in slices about 1 mm. thick 

 and of these slices about 0.1 to 0.05 grams per liter of water were added 

 to the tank containing the bran infusion. If too much bran infusion 

 or liver was added, Daphnia came to the top because of lack of oxygen. 

 It was then necessary to replace some of the old with fresh water. 



After the liver is heated it may be dried by keeping in a cool place and 

 then used as required. It has been observed that such liver slices in con- 

 tact with the water will tend to become moldy in the absence of a 

 sufficient number of Daphnia, but if enough Daphnia are present the mold 

 will disappear. Nearly all of this work was done with Daphnia magna, 

 although the above methods were found to apply to several other Clado- 

 cerans as well. 



PROPAGATING DAPHNIA AND OTHER FORAGE 

 ORGANISMS INTENSIVELY IN SMALL PONDS* 



FOR the first few years we tried to keep cultures going continuously 

 throughout the summer in the same pond, merely adding from time 

 to time a definite amount of fertilizer. The result was that very success- 

 ful cultures were maintained during May and part of June which always 

 ran out in July but seemed to come back in late September and October. 

 The most important causes for the diminishing supply seemed to be the 

 population density, the accumulation of waste products not only from the 

 Daphnia themselves but from micro-organisms also present, predatory 

 enemies of Daphnia, and probably water temperatures somewhat above 



♦Abstracted from an article in Trans. Amer. Fish. Soc. 64:205, 1934, by G. C. Embody, 

 Cornell University, and W. O. Sadler, Mississippi College. 



