396 PROCEEDINGS OF THE AMERICAN ACADEMY. 



defective in their reactions, such as No. 7 in Series A, and Nos. 4 and 

 6 in Series C, which turned in all cases to their left. This may have 

 been due to indifference to light, the animals turning to their left possi- 

 bly for some structural reasons, or there may have been some defect 

 of sight in the right eye, which would also result in a turning always to 

 the left. It should be mentioned that the same individuals, in part at 

 any rate, were used in the different series, but that the numbers by 

 which they are designated in the various sets do not correspond. For 

 this reason No. 4 or No. 6 of Series C may have been the same indi- 

 vidual as No. 7 of Series A, but it is impossible to say definitely. It 

 was found, too, that sluggish or inactive individuals, or those which 

 did not oi'ient readily to the light used for that purpose before making 

 the trial, gave in general a much smaller proportion of reactions toward 

 the large light than those frogs which reacted promptly and oriented 

 readily to the incandescent lamp. Individuals No. 5, Series ^4, and 

 No. 9, Series B, are examples of the inactive sort. 



Series D comprised 100 trials, on 13 different individuals, with the 

 lights at half the usual distance. The results are shown in Table IX, and 

 are so decided as to admit of no doubt as to the character and meaning 

 of the reactions. Of the 100 trials, 83 were toward the large light and 

 only 17 toward the small one. This means an excess of 66 per cent of 

 the turnings in the direction of the large light. This is considerably 

 larger than the corresponding value found for Ranatra (45.8 per cent; 

 cf. p. 387), but smaller than that found in the reaction of Vanessa (75 

 per cent ; cf. p. 382). It will be noticed that with the exception of indi- 

 viduals 4, 11, and 12, all the animals turned toward the large light in at 

 least three-fourths of the trials with them, that is, in at least 6 out of 8 

 trials ; and if the records of these three had been omitted, it would have 

 brought the total number of reactions toward the large light up to 93 

 per cent, or an excess of 86 percent over those in the opposite direction. 

 No memorandum appears to have been made at the time with regard to 

 the behavior of individual 4 in other respects ; but No. 11" did not 

 orient well to single [incandescent] light " and was " apparently nega- 

 tive," at least part of the time ; while No. 12 was " first positive, then 

 became negative." In correspondence with this change of behavior 

 to a single light in this last individual, it first gave 4 turnings to the 

 large light and then 4 to the small. 



It will thus be seen that the proportion of reactions to the large 

 light by Acris was considerably lowered by the inclusion of the 

 records of these three animals, which were either in a negative, or at 

 least an inconstant or indifferent, state as regarded the character of 

 their responses to one-sided illumination. As with Ranatra, this 



