268 bulletin: museum of comparative zoology. 



sensitive region. Reese (:06) obtained similar results with Crypto- 

 branchus, but he found that in Neeturus when illuminated from above 

 the head was the most sensitive part, due to stimulation received 

 through the eyes ; but that, when the ventral surface was illuminated, 

 the head was less sensitive than the tail. Payne (:07) showed that 

 sensitiveness to light was present in the skin of the blind fish Amblyop- 

 sis, and that "they seem to be equally sensitive on all parts of the 

 body." Eycleshymer (:08) found that the decapitated larvae of 

 Neeturus oriented to light in the same manner as the normal larvae do, 

 though they turned as frequently from the light as toward it, while 

 normal larvae turned usually toward the light. After decapitation, 

 the tail was the most sensitive region. More recently Pearse (:10) 

 has found that, out of nine species of amphibians, comprising anurans 

 and urodeles, which he tested, seven " after the removal of their eyes 

 gave photic responses which were like those of normal individuals." 

 The toad was one of the seven species in which Pearse found the skin 

 to act thus as a photoreceptor. It was therefore natural to expect 

 that the skin of the toad would show a sensitiveness to lights of 

 different wave-lengths. Hence it seemed desirable to test toads in 

 single monochromatic lights; first, with only the eye as receptor; 

 and secondly, with only the skin as receptor. In testing the reactions 

 with only the eye as the receptor, the method and procedure were 

 the same as described on p. 264-266, except that the beam of light was 

 made to pass through a small opening in a screen placed close to the 

 table (T), fig. 1, the opening being made of such size, and so adjusted, 

 that only the eye of the toad and a very small area of skin around it 

 were illuminated. 



The results of these tests are given in Table 2. Again three sets of 

 twelve toads each were tested, the total number of trials in each light 

 being, therefore, 288. For all three sets, the same twelve toads were 

 used that had been used in the first two sets of experiments, in which 

 both the eye and the skin served as receptors. Of the original twelve, 

 however, two individuals died in the course of the experiments, and 

 their places had to be supplied by two other toads. The nature of the 

 reactions was the same as when both the eye and the skin were exposed. 

 The toads, after the.y had turned toward the light, moved toward it, 

 so that the beam of light was kept on the eye. 



It will be seen, by referring to Table 2, that the reactions of the toads 

 when only the eye was exposed to the light were essentially the same 

 as when the whole body was exposed, and that the sequence of the 

 lights, as determined by their effectiveness in stimulating the toads, 



