THE REACTIONS OF THE MELANOPHORES OF 



AMBLYSTOMA LARVAE— THE SUPPOSED 



INFLUENCE OF THE PINEAL ORGAN 



HENRY LAURENS 



Osborn Zoological Laboratory, Yale University 



SIX FIGURES 



INTRODUCTION 



Although the hterature deahng with the chromatophores is 

 very voluminous, nevertheless there are still many points con- 

 cerning which our knowledge is far from complete. One of 

 these, and a fundamental one, because it lies at the foundation 

 of our comprehension of the physiology of the pigment cells, 

 is the relation between them and the nervous system. We 

 know much about the reactions to various stimuli of the chroma- 

 tophores of many animals but when we come to compare them 

 it is found that they are so diverse that it is almost impossible 

 to lay down any general rule which will cover all cases. In 

 some animals light causes a contraction of the pigment cells, 

 in others it has no noticeable effect, and in still others it pro- 

 duces expansion. Attempts have been made, of course, to ex- 

 plain these different results, and in the excellent review by Fuchs 

 ('14) this is often done, with, it must be admitted, not always 

 marked success. The particular case in which we are interested 

 concerns the reactions to light and to darkness of the melano- 

 phores of Amblystoma larvae. 



Babak ('10) obtained very interesting results regarding the 

 melanophores of these larvae. He found that there was a dif- 

 ference between the reactions of the pigment cells of normal 

 and bhnded Axolotl (A. mexicanum Cope, A. tigrinum Laurenti) 

 larvae to light and darkness. In diffuse light, according to Babak, 

 the melanophores of normal seeing larvae contract, those of 



237' 



