34 E. H. HARPER. 



in a definite " avoiding reaction." In this respect the effect is 

 like the response to very strong light. Consequently we see that 

 the random reactions to weaker light have a special explanation 

 and are only an apparent exception to the general form of nega- 

 tive response. 



BIBLIOGRAPHY. 

 Adams, George P. 



'03 On the Negative and Positive Phototropism of the Earthworm Allolobophora 

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Gar man, H. 



Bulletin of Illinois State Lab. of Nat. Hist., Vol. III., Art. IV. Note 

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Hesse, R. 



'96 Untersuchungen iiber die Organe der Licht-Empfindung bei niederen 

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Holmes, S. J. 



'05 The Selection of Random Movements as a Factor in Phototaxis. Journ. 

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Jennings, Herbert S. 



'04 Contributions to the Study of the Behavior of Lower Organisms. Published 

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Parker, G. H. and Arkin, L. 



'01 The Directive Influence of Light on the Earthworm Allolobophora foelida 

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'02. The Influence of Temperature, Odors, Light, and Contact on the Move- 

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 ZOOLOGICAL LABORATORY, 



NORTHWESTERN UNIVERSITY, 



EVANSTON, ILLINOIS, August 14, 1905. 



