AUTHOR S ABSTRACT OP THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, MAY 4 



THE PHYSIOLOGY OF THE MELANOPHORES OF THE 

 HORNED TOAD PHRYNOSOMA^ 



ALFRED C. REDFIELD 



From the Zoological Laboratory of the Museum of Comparative Zoology at Harvard 



College 



EIGHT TEXT FIGURES AND FIVE PLATES 



TABLE OF CONTENTS 



I. Introduction 276 



II. Melanophore reactions of the horned toad 277 



1. Description of color changes 277 



2. Daily rhythm of color changes 278 



3. Adaptive color changes 279 



4. Color changes due to nervous excitement 279 



III. External stimuli involved in melanophore reactions 280 



1. Illumination and temperature 280 



2. The color of the substratum 282 



3. Mechanical stimuli 283 



4. Faradic stimuli 283 



5. Noxious stimuli 283 



Summary 284 



IV. Receptors involved in melanophore reactions 284 



1. Direct action of stimuli upon melanophores 284 



2. Receptors of noxious stimuli 289 



3. Receptors involved in adaptive reactions 290 



Summary 291 



V. Coordinating mechanisms of melanophore reactions 291 



1. Coordinative action of the circulation 292 



a. Influence of the respiratory function of the circulation upon 



melanophores • 292 



b. The coordination of melanophores by hormones 292 



c. The nature of the hormone involved in melanophore reac- 



tions 295 



2. Coordinative action of the nervous system 306 



a. The nervous control of melanophores 306 



b. The nervous paths of melanophore reflexes 310 



Summary 312 



1 Contributions from the Zoological Laboratory of the Museum of Compara- 

 tive Zoology at Harvard College. No. 309. 



275 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 26, NO. 2 



