272 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
blue, and yellow than green, the decrease in effectiveness for the two 
pairs of lights being the same. The lights thus formed a decreasing 
series with blue as the most effective stimulus, and red as the least, this 
light being not much more effective than darkness. 
D. Reactions of Nornal Toads, compared with those of Toads from 
which the Eyes had been removed. 
In describing the method of experimentation used in exposing only 
the eye to the light (p. 268), it was stated that the eye and a very small 
area of skin around it were illuminated. It therefore seemed desirable 
to ascertain whether this small area of skin had any influence upon the 
reactions of the toads. To test this, it was decided to make use of 
only the blue light, since this had proved more effective than the other 
lights, and if no results were obtained with it to show that this small 
area of skin around the eye had any influence, it was reasonable to 
suppose that with the other lights none would be obtained. 
For these tests three toads that had not previously been experi- 
mented with were selected, and their reactions tested both in the 
normal condition, and after the eyes had been removed. Each toad 
was tested, first with the whole body, then with only the eye, and 
finally with only the skin exposed. The eyes were then removed and 
the same tests repeated. The methods and procedure were the same 
as have been previously described for each condition of exposure, 
except that a period of fifteen minutes, instead of five, was given each 
toad in which to react. No toad was experimented with for three 
days after the operation of removing the eyes. A toad from which 
the eyes had been excised very seldom hopped after turning, but 
usually crawled toward, or away from, the light. 
The results of the tests are given in Table 4. Each toad was given 
a total of sixty-four trials, but not more than eight consecutively, an 
interval of at least an hour intervening before it was again tested. 
The total number of trials for each of the three conditions of exposure 
was, therefore, 192. It will be seen, by referring to Table 4, that the 
reactions of the toads in normal condition agreed closely with those 
shown in a later Table (6), also for blue light, though there were 2 % 
more positive responses when only the eye was exposed, than when the 
whole body was exposed. This, however, is not an important de- 
parture, and would probably not be present if a larger number of 
toads had been used. The eyeless toads, when the whole body, or 
only the skin, was exposed, also showed a close agreement with the 
