MAZE STUDIES WITH WHITE RAT 293 



mainly specific rather than general; this fact eliminates the 

 3rd hypothesis as a complete explanation of the process, since 

 rats in time should become practically immune to all ordinary 

 distractions. Neither can the fact be readily envisaged under 

 the 4th and 5th conceptions ; it is most easily explicable in terms 

 of the 2nd hypothesis. A sense organ can play a part in the 

 process of adaptation although the disturbance was mediated 

 through some other sense avenue. Normal rats displayed the 

 greater adaptive power in the hunger experiment, so that vision 

 must have been concerned in the process although the disturb- 

 ing conditions were intraorganic. This fact would eliminate 

 the 5th conception as a complete explanation of adaptation. 

 The maximum adaptive power of normal rats was manifested 

 in those experiments in which the optical features of the en- 

 vironment were altered. Adaptation was very rapid when either 

 the maze or the environment was rotated in reference to each 

 other, but no adaptation was present when both maze and 

 environment were rotated simultaneously. This fact may be 

 conceived in either of two ways: 1. We may assume that the 

 eye can adapt only for visual distractions. This assumption 

 naturally suggests the 5th conception. 2. We may assume the 

 truth of the 2nd conception, and explain the inability of the 

 normal rats to adapt to the rotation of maze and environment 

 as due to the homogeneity of the visual environment in this 

 experiment. 



These conceptions are not mutually exclusive; all may con- 

 tribute to the process of adaptation. Only the first possibility 

 must be summarily dismissed. The second conception receives 

 the most support, as there are no facts which can not be ex- 

 plained in its terms. The 3rd conception meets the greatest 

 amount of difficulty; it can not account for the entire process 

 of adaptation. The evidence for and against the 5th hypothesis 

 is about equally balanced. 



CONCLUSIONS 



The white rat is sensitive to optical stimuli through the me 

 dium of the eye. 



Both advantages and disadvantages accrue from the posses- 

 sion of visual receptors in the maze situation. 



