THE REACTIONS OF THE MELANOPHORES OF 



AMBLYSTOMA TIGRINUM LARVAE TO 



LIGHT AND DARKNESS 



HENRY LAURENS 



Osborn Zoological Laboratory, Yale University 



SIX FIGURES 



INTRODUCTION 



In two earlier papers (Laurens '15 and '16) the reactions to 

 light and darkness of the melanophores of normal and eyeless 

 larvae of A. punctatum and of A. opacum were described. These 

 differed in some details from the corresponding reactions de- 

 scribed by Babak ('10) for normal and blinded Axolotl. larvae. 

 The present paper is concerned with the description of similar 

 reactions of the melanophores of larvae of Amblystoma tigri- 

 num, the tiger salamander, the so-called Axolotl. Owing to the 

 close similarity of these results with those obtained with A. 

 punctatum and A. opacum they can be briefly dealt with. A 

 few observations were also made of the melanophores of larvae 

 of A. microstomum.i These showed responses sUghtly different 

 from the others, but owing to the fact that only a few larvae were 

 available at the time the observations were made, not very much 

 can be said about them beyond the statement that the melano- 

 phores apparently do not show the secondary reactions which 

 have been described for punctatum and opacum. 



Babak ('10), it will be remembered (see Laurens '15, p. 620 

 and '16, p. 237), found that there was a difference between the 

 reactions of the melanophores of normal and blinded Axolotl 

 larvae to light and darkness. In bright diffuse light the melan- 



^ The eggs of A. tigrinum were sent to me by Prof. C. Judson Herrick, of the 

 University of Chicago, those of A. microstomum by Prof. G. E. Coghill, of the 

 University of Kansas. It is a pleasure to thank both of these gentlemen for 

 their kindness. 



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