174 LESLIE B. AREY 



The work described for living Amciurus has been repeated 

 on both Abramis and Funduhis with identical results. In every 

 case the pigment maintained the position it occupied previous 

 to the application of the anaesthetic. 



The results obtained in this study, as a whole, are very differ- 

 ent from those of Fick ('90), who concluded that the retinal pig- 

 ment of the frog expanded when the animals were subjected 

 to an atmosphere of carbon dioxide gas. Fick attributed this 

 result to asphyxiation and it is certain that the experimental 

 conditions in his work differed greatly from those in my tests. 

 In order to make the experiments more comparable, frogs should 

 be treated with a mixture of oxygen and carbon dioxide gases 

 in which they could live. 



2. Ether. The anaesthetic effect of ether on the retinal pig- 

 ment was demonstrated by a series of tests that duplicate those 

 described with carbon dioxide. Care must be observed against 

 using an excess of ether since otherwise a partial or complete 

 disintegration of the pigment cells results. 



Both dark and light trials were made on Ameiurus, Abramis, 

 and Fundulus. In each animal the pigment was found to be 

 completely arrested in whatever position it occupied at the be- 

 ginning of the experiment. Controls proved that ether, if 

 used in small amounts, does not permanently injure the pigment 

 cells. 



Ether also checked the migration of pigment in excised eyes 

 of dark-adapted Ameiurus when such eyes were subjected to light. 



3. Chloretone and ur ethane. These substances are such satis- 

 factory narcotizing agents that their effect was tested upon the 

 retinal pigment of Ameiurus. Individuals lived in 0.1 per cent 

 chloretone or in 1.0 per cent urethane, but the pigment was not 

 arrested in its movement from the dark to the light phase. In 

 concentrations of 0.5 per cent chloretone and 2.5 per cent ure- 

 thane, the pigment migrated when fish were brought from dark- 

 ness to light although the animals died in both cases. 



The results from all the foregoing experimentation are of 

 interest in showing the difference in the effect upon pigment 

 cells of four powerful anaesthetics, of which only two were 



