8o 



Scientific Proceedings (97). 



of heat and light, an effect just the opposite of that which the 

 same factors produce in the normal skin. 



Finally it may be mentioned that when all stimuli are removed 

 the resulting condition of the pigment cells does not differ greatly 

 in normal and albinous larvae. A study of animals which have 

 recently died in the aquaria, or have been purposely killed, shows 

 that the pigment cells in both normal and albinous individuals 

 come to approximately the same condition, which is one of partial 

 expansion of the xantholeucophores and an expansion of the 

 epidermal melanophores greater than can be produced by the 

 action of light or heat or other experimental means in living ani- 

 mals. The reaction of the xantholeucophores in albinous and 

 normal larvae is also identical when subjected to all the anes- 

 thetics tried by the writer (paraldehyd, chloretone, and ethyl- 

 urethan). In both they are greatly contracted. 



45 (1420) 



Upon the experimental exchange of skin transplants between 

 normal and albinous larvae. 



By P. E. Smith (by invitation). 



[From the Anatomical Laboratory, University of California.] 



If sufficient speed is exercised, an exchange of the middorsal 

 area of skin can be successfully accomplished between two frog 

 larva?, a normal one and its albinous mate. Since there are striking 

 and constant differences between two such larvae as concerns 

 both classes of superficial pigment cells, a highly interesting oppor- 

 tunity to test the influence on such cells of a new host was pre- 

 sented. Four such successful skin exchanges were accomplished 

 and in all instances definite and constant changes in the con- 

 dition of the xantholeucophores were produced as a result of the 

 exchange. The changes, which are well under way in an hour 

 after such an experiment and which have yielded harmonious 

 results, would appear to be of great value in the interpretation of 

 the change in the physiological state of these cells which albinism 

 produces. It will be recalled that the corial xantholeucophores 



