82 MARY HONORA SAYLE 



found that though all parts of the body could be stimulated by 

 white light, the head was the most sensitive region. He also 

 worked with light passed through "red" and "blue" glass, and 

 found that slow responses were thus induced. In his heat 

 experiments he found Necturus to be sensitive to considerable 

 changes in temperature. Pearse showed that Necturus is nega- 

 tively phototropic and that it comes to rest in shaded areas. 

 Both the skin and eyes act as photoreceptors, and the stimula- 

 tion of either brings about negative reactions. 



The present study endeavors to ascertain the sensitiveness 

 of the general body surface of Necturus to touch, chemicals, 

 heat, and light. 



The experiments were performed on four individuals of aver- 

 age size, though only three of them were used for the light and 

 heat experiments. Just before each experiment the individual 

 to be used was transferred from the aquarium tank into a zinc 

 tray, three by one and one-half feet. The transfer was made 

 by grasping each animal just behind the front legs. The method 

 of measuring movement employed in the experiments was a rather 

 simple one. A coarse wire screen that covered the tray was 

 divided off with twine into inch squares. It was possible in 

 this way to observe and at the same time measure the move- 

 ments of Necturus beneath the screen. 



When not being used for the experiments the animals were 

 kept in running water in an aquarium tank, six by three feet, 

 in the vivarium of the Biology Building, University of Wis- 

 consin. The tank was divided into four compartments, one for 

 each animal. Bricks and strips of wood were used to make 

 suitable dark nooks like the natural haunts of Necturus. 



This work was accomplished under the direction of Professor 

 A. S. Pearse, for whose helpful suggestions and encouragement 

 it gives me great pleasure to express my appreciation. 



REACTIONS TO TOUCH 



The whole outer surface of Necturus is open to stimulation 

 from a deforming pressure, that is, it is sensitive to touch. 

 Animals were tested for touch sensitiveness with wood, glass, 

 and a soft brush. 



A blunt piece of wood the size of an ordinary pencil was 

 touched gently to various regions of the body. When any 



