CONTRIBUTIONS FKOM THE ZOOLOGIC.VL LAJBORATORT OF THE MUSEUM OF COMPAKATIVE ZOOLOQT AT 



HABVARD COLLEGE. NO. 278, AND FROM THE ANATOMICAL LABORATORY OP THE NORTHWESTERN 



UNIVERSITY MEDICAL SCHOOL, NO. 36. 



THE INFLUENCE OF LIGHT AND TE:\IPERATURE 



UPON THE MIGRATION OF THE RETINAL 



PIGMENT OF PLANORBIS TRIVOLVIS 



LESLIE B. AREY 



NINE FIGURES 



CONTENTS 



Introduction and historical survey 359 



Material and methods 362 



Description of the eye of Planorbis 365 



Experimental part 369 



a. Effect of light and darkness 369 



1. Effect on normal animals 370 



2. Effect on excised eyes 371 



b. Determination of adaption times 374 



c. Effect of temperature 376 



1. Effect on normal animals 376 



2. Effect on excised eyes 377 



d. Effect of anaesthetics 378 



Discussion 379 



Summary 385 



Bibliography aS6 



INTRODUCTION AND HISTORICAL SURVEY 



The pigment granules of many animal cells, wliich in general 

 are termed melanophores, are capable of undergoing positional 

 changes when adequately stimulated. This property has made 

 possible the development of an interesting field of research, 

 which has had for its goal, the correlation of migratory move- 

 ments of the pigment with the presence of definite stimulatmg 

 agents. At first, only the influence of such important environ- 

 mental factors, as light and temperature, as well as the effects 

 of more artificial stijuulating agents like pressure and electricity 

 were sought, and but Uttlc attention was given to the role played 

 .by chemical agents. Recently, however, the possibility of 



359 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 26, NO. 4, 

 AUGUST, 1916 



