RESPONSES OF YOUNG TOADS 207 



the definition of Jennings (1909, p. 307), however, the writer 

 does not wish to be understood as believing that internal fac- 

 tors, changes in bodily states, play no role in the orientation 

 of young toads to light. This matter was not discussed in con- 

 nection with the responses to intense artificial light, largely 

 because the wi\ter was attempting to record the responses as 

 they occurred in the majority of cases. There are occasional 

 examples when it is observed that one toad orients to the light 

 much more slowly and hesitatingly than another. Some toads 

 jump away from the light more rapidly than others and along 

 a straighter path. There also is found to be variations in such 

 responses on the part of the same animal on different occasions. 

 These facts seem to indicate modifications in the bodily condi- 

 tions of the animals concerned, especially when it is remem- 

 bered that both the environment and the kind of stimuli remain 

 unchanged. Loeb (I.e., p. 24) and (1912, p. 47) early recog- 

 nized the importance of differences in the physiological condi- 

 tions of animals as modifying factors in animal responses. This 

 subject has been discussed by the present writer (191 2, pp. 

 281-283). It is not improbable, in the writer's experiments 

 with young toads, that before orientation the animals are, as 

 it were, in a condition of unstable equilibrium with refer- 

 ence to the light, and that the orienting response is one 

 of adjustment; and further, after orientation is completed the 

 toads are then in a condition of relative stability toward the 

 light, so far as orientation is concerned, and they exhibit further 

 response by jumping away from the source of illumination. 

 With reference to orientation in general, may it not be a fact 

 that previous to the orienting response the bodily state of the 

 animal differs from its condition after orientation is complete? 

 The responses of young toads to the light from the projec- 

 tion lantern seem to indicate that the unequal light intensity 

 on the two sides of the body is a factor in inducing the animals 

 to orient so promptly and definitely. According to Holmes 

 (1907, p. 346), frogs orient with respect to light in general in 

 much the same manner. Pearse (I.e., pp. 172-205) apparently 

 takes a similar point of view with reference to the orientation 

 of specimens (some of them immature) of Bufo americanus and 

 Bufo fowleri to light of 220 ca.m. intensity (see particularly 

 I.e., pp. 204-205). The orientation of specimens of B. ameri- 



