THE EFFECT OF TEMPERATURE ON THE PHOTOTROPIC 

 RESPONSE OF NECTURUS. 



By WILLIAM H. COLE. 



{From the Biological Laboratory of Lake Forest College, Lake Forest, Illinois) 



(Received for publication, February 6, 1922.) 



It is a well known fact that Necturus maculosus is negatively 

 phototropic. According to Eycleshymer (1906, 1908, and 1914) 

 Reese (1906), and Pearse (1910), the animal always avoids sunlight 

 in its natural environment as well as in the laboratory. They 

 conclude that the skin is the important receptor for the photic stimu- 

 lus since eyeless animals behave similarly to normal ones. It is also 

 known that Necturus is sensitive to temperatures below 5° and above 

 25°C. (Reese, 1906; Sayle, 1916). I have found that the animals 

 become more active when transferred from a temperature of 20° to 

 one of 2°C., but that after several hours of exposure to the low tem- 

 perature, they become very sluggish. As the temperature increases 

 they show increased activity until death ensues between 35° and 40°C. 

 Violent spasmic movements are characteristic of such high tempera- 

 tures previous to death. 



When illuminated, therefore, it may be assumed that the reaction 

 time of Necturus will vary according to the intensities of the thermal 

 and photic stimuli. The experiments reported here were performed 

 to determine the effect on the reaction time of variations of the tem- 

 perature in normal and eyeless animals, and to express it in quanti- 

 tative form. 



The animals were kept in a large aquarium with running water at 

 20°C. They were thus adapted to light of very low intensity and to 

 a medium temperature. The animals were tested singly in a dark 

 room, where the temperature and the light intensity could be easily 

 controlled. They were placed in a rectangular blackened dish (170 

 cm. long, 11 cm. wide, and 8 cm. deep), and allowed 15 minutes for 

 acclimatization. At the beginning of each trial, the animal was ori- 

 ented in the center of the dish, with the longitudinal axes of the animal 



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