REACTIONS OF CRAYFISHES. 



but not so definitely to high total concentrations ; diogenes reacts 

 irregular and less intense than the first two species while immunis 

 reacts more definitely but with low intensity. 



8. All four species react more strongly to hydrochloric acid 

 than acetic acid and more strongly to acetic acid than carbon 

 dioxide. 



9. The intensity of avoiding reactions of all species to all 

 acids tested as is shown by turnings only are in the following 

 order; propinquus, virilis, immunis and diogenes. 



10. The intensity of avoiding reactions of all four species 

 varies directly as the total concentrations of the acids, and 

 probably directly as the hydrogen ion concentration. 



1 1 . Rapid modification of behavior is shown by all four species. 

 This modification may be due to the increased sensitiveness on 

 the part of the animals, the increased sensitiveness being the 

 result of higher ion concentration in the animal's blood. 



12. The specific reactions of the crayfishes in gradients of 

 carbon dioxide may be correlated with their habitats. 



ACKNOWLEDGMENTS . 



I wish to express my appreciation and sincere thanks to Dr. 

 V. E. Shelford, under whose direction this work was undertaken, 

 for his constant help and many suggestions; also to Mr. M. M. 

 Wells for assistance in determining the species of crayfishes used, 

 and for suggestions during the performing of the experiments 

 and writing of the manuscript. 



TRINITY UNIVERSITY, 



WAXAHACHIE, TEXAS. 



BIBLIOGRAPHY. 

 Abbott, C. C. 



Notes on the Habits of Certain Crayfishes. Am. Nat., Vol. 7, pp. 80-84. 

 Bell, J. C. 



'06 The Reactions of Crayfishes to Chemical Stimuli. Jour. Comp. Neur. 



and Psychol., Vol. 14, pp. 229-326. 

 '12 The Reactions of the Crayfishes. Harvard Psychological Studies, Vol. 2, 



pp. 615-644. 

 Chidester, F. E. 



'12 The Biology of the Crayfishes. Am. Nat., Vol. 46, pp. 279-293. 



'08 Notes on the Daily Life and Food of Cambarus bartonius bartonii. Am. 



Nat., Vol. 42, pp. 710-716. 



