RESPONSES OF YOUNG TOADS 183 



and they remained in this position although the light was en- 

 tirely unbearable to the human eye. 



In connection with the responses of young toads both in and 

 out of water, it would have been extremely interesting to have 

 used a much longer experimentation trough in order to demon- 

 strate whether or not the animals were seeking a certain opti- 

 mum intensity of illumination. The writer planned to perform 

 experiments of this nature if more material had been available 

 at the time, and he hopes to do so in the future. 



In connection with these responses of young toads to intense 

 light, it is of interest to recall the work of Pearse (1910) relative 

 to frogs and toads. This writer (I.e., p. 175) found that Rana 

 clamata moved toward a light of 225 ca.m. from a six-glower 

 Nernst lamp. Five specimens were subjected to the light. 

 He also states (I.e., pp. 175-176) that Rana sylvatica was ex- 

 posed to photic stimuli from a light of the same intensity. His 

 results are summed up in the following quotation (I.e.): 



"This frog was more active than the last species, [R. clamata] and 

 some individuals gave more decided phototropic reactions than did any 

 member of the preceding species. There were, however, such differences 

 in the reactions of the four animals used that they are tabulated sepa- 

 rately. Individual No. 1 never failed to move straight toward the light. 

 No. 2 was not as persistently positive after the eyes had been excised as 

 before this operation, though it continued to give a majority of positive 

 reactions. As individuals 3 and 4 were apparently indifferent to the light 

 in their normal conditions, their eyes were not removed. The reactions 

 of animals 1 and 2 were, however, strongly positive, and this condition 

 remained even after the eyes had been excised ; hence their skins served 

 as photoreceptors as well as their eyes." 



These results with frogs are quite, different from the results of 

 the writer with young toads. Such differences, however, are 

 not at all surprising when it is recalled that not only are ani- 

 mals of different genera being considered, but also of different 

 families ; and further it must be kept in mind that on the one 

 hand mature organisms are under observation and on the other 

 very immature ones. Pearse (l.c,. p. 176) also experimented with 

 Bnfo americanus and Bufo fowleri. The records of the two spe- 

 cies were not kept separate. The toads respond positively to 

 a light of 225 ca.m., moving toward the source of illumination. 

 Most of the animals used were adults, but a few were immature. 

 None of them, however, were less than 2 cm. long. It has been 

 demonstrated that the present writer finds young toads to 

 respond negatively to the light from a projection lantern. The 



