LIGHT REACTIONS OF NEWT 31 



taken on three different days; and after observations 5, 7 and 17 

 the light and dark ends were suddenly interchanged, thereby 

 throwing the larger proportion of the animals, that had collected 

 in the shadow, into the light. The last five observations were 

 made about two weeks after the first, during which time three 

 of the animals had escaped. 



TABLE I 



Observation. . . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 



Light half 232220012042252 



Dark half 10 9 10 10 10 12 12 11 10 12 8 10 10 7 10 



Observation. . . 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Totals 



Light half 126454354148955 95 



Dark half 11 10 6 8 7 8 9 7 8 11 5 1 4 4 250 



Another set of observations made under the same conditions, 

 except that only enough water to moisten the bottom of the 

 aquarium was used, gave 141 animals in the light to 243 in the 

 dark region. As noted above, without enough water to swim 

 in the newts are so sluggish that experimentation is not nearly 

 so satisfactory as when they are actively swimming. 



It is evident, then, that, at least under the conditions of the 

 experiment, these newts are negatively phototropic. 



Experiment II. — Variations of experiment I were tried to de- 

 termine the effect of temperature upon the phototropic reac- 

 tions of Diemyctylus. 



The first variation was merely to start the observations, made 

 upon eleven animals, with the water at 10° C, the arrangement 

 of aquarium and lights being as in experiment I. Not only 

 was the aquarium surrounded by black, but the experiment was 

 performed in a photographic dark room. Beween the 15th 

 and 16th observations was an interval of two hours, during 

 which time the animals were in the dark. After the 30th obser- 

 vation, when all the animals were in the dark half of the aqua- 

 rium, the ends were reversed, throwing all the animals into the 

 light half. When the animals, as in this case, were sluggish it 

 would be some time before they would move into the dark 

 again, which would reduce the total preponderance of dark over 

 light. The total figures for 40 observations were 174 in the 

 light end to 278 in the dark, which was about the proportion 

 noted in experiment I when no water was used. At the end of 



