CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF 

 THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 

 COLLEGE. E. L. MARK, DIRECTOR. NO. 206. 



THE REACTIONS OF AMPHIBIANS TO LIGHT. 



By A. S. Pearse. 



Presented by E. L. Mark, December 8, 1909. Received November 24, 1909. 



TABLE OF CONTENTS. 



PAGE 



I. INTRODUCTION 162 



A. Historical 162 



B. Methods 167 



II. OBSERVATIONS 16S 



A. The Photic Reactions of Normal Amphibians compared 



WITH THOSE FROM WHICH THE EYES HAVE BEEN REMOVED 168 



(a) Necturus maculosus 168 



(b) Cryptobranchus allegheniensis 170 



(c) Ambly stoma punctatum 173 



(d) Plethodon cinereus erythronotus 173 



(e) Diemyctylus viridescens 174 



(/) Rana clamata 175 



(g) Rana sylvatica 175 



(h) Bufo americanus and B.fowleri 176 



(i) Conclusions 177 



B. The Influence of Mechanical Stimulation on the Photic 



Reactions of the Toad 177 



C. The Reactions of the Toad to Photic Stimulation through 



the Eyes alone 178 



D. The Reactions of Eyeless Toads to Unilateral Stimula- 



tion by Light from above 182 



E. The Effects of Illuminating Small Areas of Skin on Eye- 



less Toads 183 



F. The Effect of Previous Conditions of Light Stimulation 



on Photic Reactions 184 



G. The Reactions of Amphibians to Lights of Different 



Colors 187 



(a) Normal individuals 188 



(b) Eyeless individuals 189 



(c) Summary 191 



VOL. xlv. — 11 



