270 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
in such a way that the eyes were completely covered. These hoods 
were attached by two threads to a light copper wire, which encircled 
the animals’ bodies just back of the fore-legs. To insure that no 
light penetrated these hoods, they were blackened inside and out 
with India ink. The extreme tip of the hood was cut off so that respi- 
ration should not be interfered with. 
The hoods were at first a source of some irritation to the toads, 
which struggled more or less to get rid of them. In a day or two, how- 
ever, the toads showed no inconvenience when the hood was slipped on, 
but remained quietly seated on the bottom of the battery-jars in 
which they were kept (p. 263). In testing the reactions, the methods 
and procedure of the experiments were the same as described on p. 
264-266. 
The results of these tests are given in Table 3. Four sets of twelve 
toads each were tested, the total number of trials for each light being, 
therefore, 384. For the first two sets, six of the twelve toads were the 
same as had been used in the first two sets of experiments in which the 
eye and skin acted as receptors, and in the three sets of experiments 
TABLE 3. 
Reactions of toads to monochromatic light received through the skin only. 
| 
Monochromatic Blue | Green | Yellow | Red 
lights of equal | | | 
intensity 420-480 ww =| 490-550 uu = 5570-620 wp | 630-655 uu 
Directions of | + |—|+} 0} + }— +|/0/ + |—|+|0/ 4+ | —|4]0 
oa ne, ine oa. 
£ | Number of | | | | 
i responses | 296 | 88 271 \113 248 136 | 217 | 1166/1 
<= | Percent of | | 
responses | 77 23 | ea 29...” | 65 | 35 57 |, 43 
| | | | 
| | 
The numbers under + indicate total numbers of reactions toward the light; 
under—, away from the light; under +, without reference to the light (indifferent) ; 
under O, no reaction within five minutes. 
in which the eye acted as the receptor; the other six were toads which 
were supplied to take the place of six that had died during the course 
of the experiments. For the last two sets, two new lots of twelve 
