ENVIEONMENT ON ARCELLA 441 



LITERATURE CITED 



Hegner, R. W. 1919 Heredity, variation and the appearance of diversities 



during the vegetative reproduction of Arcella dentata. Genetics. 



Vol. 4, pp. 95-150. 



1920 The relations between nuclear number, chromatin mass, 



cytoplasmic mass, and shell characteristics in four species of the 



genus Arcella. Jour. Exp. Zool. (In press.) 

 Jennings, H. S. 1916 Heredity, variation and the results of selection in the 



uniparental reproduction of Difflugia corona. Genetics, vol. 1, pp. 



407-534. 

 Leidy, J. 1879 Fresh-water rhizopods of North America. Report U. S. Geol. 



Survey of the Territories, 12, 324 pages. 

 Root, F. M. 1918 Inheritance in the asexual reproduction of Centropyxis 



aculeata. Genetics. Vol. 3, pp. 174-206. 

 Whitney, D. D. 1916 The transformation of Brachionus pala into Brachionus 



amphiceros by sodium silicate. Biol. Bull., vol. 31, pp. 113-120. 



