OBSERVATIONS ON THE REACTIONS OF CRYPTO- 



BRANCHUS AND NECTURUS TO LIGHT 



AND HEAT. 



A. M. REESE. 



During most of the time for the past four years the writer has 

 had one or more specimens of the giant salamander (C. allc- 

 ghcnicnsis] in captivity in the laboratory, and the tendency of 

 these animals to seek the darker parts of the tanks in which they 

 were confined, or to crawl under any sufficiently large object that 

 might be present, led to the experiments which are summarized 

 in the present paper. 



The experiments with Xcctitrns were performed on five indi- 

 viduals of average size, though most of the light experiments 

 were carried on upon one individual. 



Four large specimens of Cryptobranchus were used for both 

 sets of experiments, the heat experiments being nearly all per- 

 formed after the completion of the light experiments. 



In the light experiments three sources of illumination were 

 employed : A sixteen candle-power incandescent electric lamp, so 

 shaded that the light could be thrown on any given part of the 

 animal without illuminating the rest of the tank ; the direct rays 

 of the sun, reflected from a small mirror ; and an ordinary arc, 

 projection lantern, which was set up at the side of the tank, so 

 that a narrow beam of light could be reflected from a mirror 

 into the wateh 



In the color experiments red and blue globes were used with 

 the incandescent lights, and with the other two methods of illumi- 

 nation plates of red and blue glass were introduced into the white 

 rays from the sun or from the electric arc. 



It was found, by the use of the spectroscope, that the red 

 plate gave an almost pure red, while the red bulb gave, besides 

 the red, some yellow and green rays. The blue plate gave the 

 entire spectrum except the dark green, yellow and yellowish red ; 

 the blue bulb gave the entire spectrum, which apparently differed 



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