Sididae and Daphniidae 213 



interfered with the free movement of the Daphnia and often resulted in 

 their death, but by a dilution of 1 part of the strained fluid as decanted 

 from the original mixture with 100 parts of filtered pond water a medium 

 was obtained which remained clear and in which Daphnia grew rapidly 

 and produced normal clones. It has been found desirable to renew the 

 media in which the cultures of animals are growing from time to time, 

 i.e., at periods of a week or more, but the addition of more bacteria to 

 the cotton seed medium, as suggested for manure infusions by Stuart 

 and Banta, has not been found necessary. Fresh stock supplies of the 

 cotton seed mixture have been prepared each week, a small amount of an 

 old mixture being added each time to insure inoculation with the original 

 bacteria. 



References 

 For the culture of Cladocera see also p. 136. 



Bibliography 



Banta, A. M. 1921. Science 53:557. 



Stuart, C. A., and Banta, A. M. 1931. Physiol. Zool. 4:72. 



Wiebe, A. H. 1930. Bull. U. S. Bur. Fish. 46:137. 



M. E. D. 



A CULTURE MEDIUM FOR DAPHNIA* 



FLEISCHMANN'S yeast has been fed to a mass culture of Daphnia 

 magna with striking results, reproduction and growth being markedly 

 more rapid, and population more dense than with any of the usual media. 

 About Y 4 of a fresh yeast cake is mixed into a uniform suspension with 

 from 50 to 100 cc. of water, and poured into the aquarium, which con- 

 tains from 60 to 70 liters of water. The feeding is repeated every 5 or 

 6 days. It is necessary to have a stream of air bubbling through the 

 medium at all times, or the yeast may prove lethal, probably by giving 



off C0 2 . 



The method has not been tried on other species of Cladocera, except 

 Moina affinis, with which it was equally successful, nor has it been tried 

 with few animals in small containers, but it is so successful in the mass 

 culture that it seems wise to make the food material known. It should 

 be particularly useful in physiological work, in which the usual manure 

 infusion may be a source of large quantities of unknown solutes. It 

 should also be valuable in raising Daphnia in large numbers as food for 

 other organisms. 



M. E. D. 



♦Reprinted, with slight changes, from Science 79:60, 1934. by R. M. Bond, Santa 

 Barbara School, Carpintcria, California. 



