THE REACTIONS OF CRAYFISHES TO GRADIENTS OF 



DISSOLVED CARBON DIOXIDE AND ACETIC 



AND HYDROCHLORIC ACIDS. 1 



EDWIN B. POWERS. 



TABLE OF CONTENTS. 



I. Introduction 177 



II. Material and Methods 178 



1. Apparatus and Methods of Experimentation 178 



2. Stock 1 79 



3. Habitat 179 



4. Senses 180 



III. The Sensing of Carbon Dioxide and Acetic and Hydrochloric Acids 181 



IV. The Effect of Carbon Dioxide and Acetic and Hydrochloric Acids 181 



1. The Effect on Reflex of the Crayfishes 181 



2. Anaesthesia and Death 182 



V. Reaction and Modification in Gradients 183 



1. Carbon Dioxide Gradient 185 



(a) C. propinqnus 185 



(b) C. virilis 189 



(c) C. diogenes 189 



(d) C. immunis 189 



2. Acetic Acid Gradient 190 



(a) C. propinqnus 190 



(b) C. virilis 191 



(c) C. diogenes 192 



(d) C. immunis 192 



3. Hydrochloric Acid Gradient 192 



4. A Comparison of the Reaction of the Four Species of Crayfishes 

 Tested 194 



VI. General Discussion 194 



Summary 198 



Acknowledgments 199 



Bibliography 199 



I. INTRODUCTION. 



The following experiments were undertaken to determine the 

 reactions of crayfishes to gradients of acids, and, if possible, to 

 determine the relation of the distribution of carbon dioxide 

 contained in water to the natural distribution of the crayfishes. 

 It was also hoped that something might be added to the present 

 knowledge of the physiology of rapid modification of animals in 



1 From the Hull Zoological Laboratory, University of Chicago. 



177 



