286 ALFRED C. REDFIELD 



merit has been performed in various ways and has yielded variable 

 results. In a few cases the outcome has been in good agreement 

 with the expectation raised by the experiment just described. 



August 24., .1915. A horned toad, having the melanophore pigment 

 expanded, was tied to a board and covered with a piece of black woolen 

 cloth. Through a hole in this cloth a portion of the right half of the 

 back was exposed to the light. 



2.45 P.M. Placed in sunlight. 



3.00 P.M. Exposed part of back unchanged. Melanophore pigment 

 of unexposed part of skin is contracted. 



3.15 P.M. Body completely covered with black woolen cloth, 



3.30 P.M. Melanophore pigment of entire skin contracted. 



August 24, 1915. A horned toad, having its melanophore pigment 

 completely contracted, was tied to a board and covered with black 

 woolen cloth. Through a hole in the cloth 1 sq. cm. of the anterior part 

 of the left side of back was exposed to the light. 



2.40 P.M. Placed in sunlight. 



3.00 P.M. Melanophore pigment of exposed part of skin has expanded; 

 unexposed skin is still pale. 



From these experiments it is again evident that the illumina- 

 tion of a restricted area of the skin will cause an expansion of the 

 pigment of that area, without regard to the illumination of the 

 rest of the body or to the reactions of melanophores of the other 

 parts of the skin. 



Similar experiments have been performed in which heat was 

 used instead of light as a local stimulus. The temperature of a 

 few lateral scales could be modified by the following method. 

 Against the side of the body of a horned toad a nozzle was applied 

 through which ran a current of water of the desired temperature. 

 The nozzle was made of a piece of glass tube 2 cm. in diameter. 

 In one end was inserted a rubber stopper carrying an inlet and 

 outlet tube and a thermometer. Over the other end a piece of 

 sheet rubber was tied loosely. When pressed against the skin of 

 a horned toad, the rubber end of the nozzle wrapped itself snugly 

 about the scales and soon imparted to them a temperature which 

 must have approximated that of the water within the nozzle. 



December 15, 1913. Water at a temperature of approxuuately 45°C. 

 was passed through the nozzle applied to the right side of a horned toad 

 the melanophore pigment of which was expanded. The experiment was 

 performed in the dark so that the exclusion of light from the skin by the 



