54 C. H. TURNER. 



in the Loebian sense. These investigations prove that the move- 

 ments mentioned are caused by the directive power of some body 

 of water and not by gravity, nor the sun's rays, nor contact 

 stimuli, nor odor trails. As to whether they are responses to 

 sensations or are merely tropisms it has nothing to say. Either 

 interpretation seems equally plausible. 



7. Although the board was protected from the direct rays of 

 the sun, almost all of the species used exhibited a marked tend- 

 ency to move away from that portion of the board which was 

 nearest the position of the sun. Since the sun's rays did not 

 impinge on the individuals, this avoidance cannot be a negative 

 phototropism. It must be a form of differential sensitivity. 

 Perhaps it should be called negative photosensitivity. 



REFERENCES. 



1. Bouvier, E. L. 



'22 Psychic Life of Insects, pp. 23-24. 



2. Holmes, S. J. 



'n Evolution of Animal Intelligence, pp. 11-60. 



3. Washburn, Margaret Floy. 



'17 The Animal Mind, Second edition. 



4. Weiss, H. B. 



'14 Notes on the Positive Hydrotropism of Gerris Marginatus Say and Din- 

 eutes assimilis Aube. Canadian Entomologist, Vol. 46, 1914. 



