MODIFICATION OF THE BEHAVIOR OF FISHES 29 



is too small to make the slight difference more than a chance one. 

 The comparison of the reactions in the experiment with those of 

 the succeeding controls only serve to emphasize former findings 

 that the solute is the chief guide in the reactions of the fishes. 



Special investigation would be necessary to determine whether 

 or not associative memory plays any role, but if so, it might be 

 due to an association of increasing stimulation with stronger 

 stimulation further on in the gradient. There is a more or less 

 distinct rhythm of the reactions in the gradients and the view 

 of associative memory applied to this phase of the reaction 

 would call for a make and break of associations so rapid as to 

 cast doubt upon this being the entire explanation. And, since 

 the increased sensibility due to repeated stimulation is explain- 

 able otherwise, the assumption of learning, as applied to this as- 

 pect of behavior, is as unnecessary as it is questionable. Still, 

 while we have thus separated the type of modification here des- 

 cribed from associative memory by the use of the usual criteria, 

 we do not mean to imply that the processes involved are neces- 

 sarily fundamentally different. 



IV. ACKNOWLEDGMENTS AND BIBLIOGRAPHY 



The authors are indebted to Dr. Harvey A. Carr, Dr. Tashiro 

 and to Mr. M. M. Wells for suggestions during the preparation 

 of the manuscript. 



BIBLIOGRAPHY 



For further citations, see Shelford and Allee, 1913. 



Araki, T. Ueber die Bildung von Milchsaure und Glycose im Organismus bei 

 1891. Sauerstoffsmangel. Zeit. f. Physiol. Chem., XV, p. 335. 



Baglioni, S. Zur Vergleichenden Physiologie der Atembewegungen der Wirbel- 

 1910. tiere. Ergeb. der Physiol, Vol. 9, pp. 90-137; 1911, Vol. 11, pp. 

 526-597. 



Bethe, A. Algemeine Anatomie und Physiologie des Nervensystems. Leipzig. 

 1903. 



Cushny, A. R. Pharmacology and Therapeutics, 10th edition, pp. 498-501 Phila- 



1910. delphia. 



Edinger, L. Haben die Fische ein Gedachtniss? Allg. Zeiiung. (Trans in Smith- 



1899. sonian Rep., 1899, p. 375.) 

 Fedman, I. and Hill, L. The influence of oxygen inhalation on the lactic acid 



1911. produced during hard work. Jour. Phys., Vol. 42, pp. 439-443. 

 Fletcher, W. M. The survival respiration of muscle. Jour. Physiol., Vol. 23, 



1898. pp. 10-99. 

 Hopkins, R. and Dennis, N. Interrelation of the Ammonia and Carbon dioxide 



1911. Content of the Blood. Jour. Bio. Chem., Vol. 10, pp. 407-415. 

 Holmes, S. J. Evolution of Animal Intelligence. New York. 



1911. 



