378 LESLIE K. AREY 



Tlio ivsiilts tlnis tabulated arc so similar to those just discussed 

 in the case of normal animals that comment is scarcely neces- 

 sary. The specimens used were rather undersized and this 

 probably accounts for the low values obtained in each set. 



Unfortunately no material was available when temperature 

 experiments upon dark-adapted excised eyes might have been 

 performed. Had an influence of temperature been proven 

 under these conditions it would have been of considerable in- 

 terest, inasmuch as darkness was found (p. 371) to be ineffective 

 upon excised eyes which had previously been subjected to light. 

 This result was indeed realized in my work (Arey, '16^) upon 

 the isolated eyes of fishes, thereby suggesting that temperature 

 is a more efficient stimulating agent than is light. 



(d) Effect of anaesthetics 



In a few instances only, have clear cut observations been 

 recorded as to the anaesthetic action of definite substances upon 

 retinal pigment cells. Ovio ('95) and Lodato ('95) agreed that co- 

 caine arrested pigment migration in the frog. The writer (Arey, 

 '16^) has found that carbon dioxide or ether, without perma- 

 nently injuring the retinal pigment cells of fishes, is capable 

 of arresting completely the movements of the pigment in light 

 as well as in darkness. Chloretone and urethane, on the con- 

 trary, although of sufficient strength to kill the animals as or- 

 ganisms, did not prohibit pigment migration. Since 5 per cent 

 solutions^ of carbon dioxide effectively controlled these migra- 

 tions, it was suggested that this, the commonest of catabolic 

 products, might well be the effective agent in preventing mi- 

 gratory movements of the pigment in excised eyes.^ It is pos- 

 sible that the results, already presented, in which it was found 

 that the pigment of the isolated eyes of Planorbis migrated in 

 light but not in darkness, may be interpreted in a similar manner. 



- No attempt was made to ascertain the minimal concentrations which would 

 accomplish this end. 



3 Of four fishes used, Ameiurus, Abramis, Carassius, and Fundulus, the retinal 

 pigment of the excised eyes of Ameiurus changed its position in tlie light, where- 

 as in none of these species did a change occur in darkness. 



