hurwitz. — the reactions of earthworms to acids- 81 



Summary. 



1. The responses of the earthworm Allolobophora foetida to sohi- 

 tions of acids may be ascribed to the hydrogen ions that they contain. 



2. The reaction-time of the earthworm depends upon the number of 

 hydrogen ions present in the solution of the acid. 



3. Using the reaction-time as a basis, the earthworm was found to 

 discriminate more certainly than man between solutions of acids at a 

 concentration of 5^^. 



4. The response of the earthworm to solutions of acetic acid was 

 more active than would have been anticipated from the degree of disso- 

 ciation of this acid, and in this respect the earthworm's reactions are in 

 agreement with human sensations as worked out by Kahlenberg, and 

 by Richards. 



Bibliography. 

 Jennings, H. S. ^^'ly 



: 06. Modifiability in Behavior. II. Factors determining Direction ana 

 Character of Movement in the Earthworm. Jour. Exp. Zool., vol. 

 3, no. 3, pp. 435-455. 

 Kahlenberg, L. 



: 98. The Action of Solutions on the Sense of Taste. Bull. Univ. Wiscon- 

 sin, sci. ser., vol. 2, no. 1, pp. 1-31. 

 Parker, G. H., and C. R. Metcalf. 



:06. The Reactions of Earthworms to Salts: a Study in Protoplasmic 

 Stimulation as a Basis of Interpreting the Sense of Taste. Amer. 

 Jour. Physiol., vol. 17, no. 1, pp. 55-74. 

 Richards, T. W. 



: 98. The Relation of the Taste of Acids to their Degree of Dissociation. 

 Amer. Chem. Jour., vol. 20, pp. 121-126. 



VOL. XL VI. 



