210 C. F. CURTIS RILEY 



109) that might apply here as a partial explanation, for a por- 

 tion of the rays are parallel with each other and. with the median 

 longitudinal axes of the bodies of the toads. In the experi- 

 ments in the dark room the principal object in the toad's field 

 of vision is the light, and it is probable that the animals jump 

 toward it because they see it, an idea that has been mentioned 

 before. The light also may act continuously as Mast (I.e.) has 

 suggested, and somewhat as Loeb (1890, p. 90) stated more than 

 twenty years ago with reference to frogs when diffuse daylight 

 was used as a stimulus. The following quotation gives Loeb's 

 point of view: 



"Dass auch beim Frosch das Licht als konstante Reizursache wirkt, 

 geht daraus hervor, dass die Thiere dauernd an dem der Lichtquelle ent- 

 gegengesetzten Ende des Kastens sitzen bleiben." 



In experiments with weak diffuse daylight, orientation is not a 

 prominent feature in behavior, but there is some evidence of a 

 tendency for the toads to gather toward the source of illumina- 

 tion. 



Many of the responses of young toads to contact stimuli are 

 probably adaptive ones, such as creeping under and between 

 objects. Even so peculiar a response as that of the death-feint 

 may be of such a nature, as the observations of some writers 

 seem to indicate. It is true that in the case of some of the 

 Arthropods, it is rather more difficult to see how the death- 

 feigning response serves any adaptive purpose. The act of crouch- 

 ing against the ground and of inflating the lungs with air may 

 be another example of a protective device. It would be of con- 

 siderable scientific interest, for some investigator to make a long 

 and varied series of observations with reference to the contact 

 responses of young toads, and see in how many instances such 

 responses were adaptive in function. 



X. SUMMARY 



Specimens of Bufo americanus Le Conte, approximately 14 mm. 

 in length were collected near Ann Arbor, Michigan. They 

 respond negatively to the light from a projection lantern, with 

 an approximate illumination of 10,000 ca.m. within the field 

 of experimentation. The animals jump away from the light 

 toward the opposite end of the dish. If they are left in that 



