RHEOTAXIS IN ASELLUS. 97 



The rheo tactic reaction of Asellus can be experimentally con- 

 trolled by varying the oxygen and carbon dioxide tension within 

 the limits found in the two classes of habitats. This is not true 

 of similar variation in salt content, or in any other factor or 

 group of factors yet studied. 



LITERATURE CITED. 

 Alice, W. C. 



'12 An Experimental Analysis of the Relation between Physiological States and 



Rheotaxis in Isopoda. Journ. Exp. Zool., Vol. 13, pp. 269-344. 

 'i3a Further Studies on Physiological States and Rheotaxis in Isopoda. Journ. 



Exp. Zool., Vol. 15, pp. 257-295. 

 '16 Chemical Control of Rheotaxis in Asellus. Journ. Exp. Zool., Vol. 21, pp. 



163-198. 

 Shelf ord, V, E. 



'13 Animal Communities in Temperate America. Univ. of Chicago Press. 



362 pp. 



