A DEFINITION OF FORM 



137 



under the conditions as described in my paper, 3 the visible stimuli 

 presented to the animals for discrimination were forms not 

 patterns. On page 66 I state that the whole apparatus was set 

 up in a dark-room. I follow this with an explanation of the only 

 sources of illumination. On page 98 appears the plan of con- 

 trolling all light factors. Now, in these conditions of control, 

 there is to be found a refutation of the point which Hunter 

 seeks to establish. The rectangular tunnel, to be sure, remains, 

 but the perceptibility of the environment is wholly changed, if 

 not destroyed. That the animals could not see the environment 

 is attested by the fact that they were frequently observed to 

 walk blindly into the confining walls. Not all of the time was 

 the environment " darkened," but the control tests were always 



Figure 2 



made to determine whether or not, among other factors, setting 

 was a factor in discrimination. 



Figure 1 does not accurately illustrate the condition of the 

 stimulus areas. With the introduction of a screen between the 

 general illumination and the electric boxes and with the re- 

 duction of the intensity of the source lights, a condition similar 

 to that illustrated in figure 2 appears. In the compartment 

 where the triangle appears, the source light fails to illuminate 

 the corners of the tunnel, and so the perceptible portion of the 

 setting changes to a sort of circular form as in diagram 1 . About 

 the circular stimulus the visible setting is more nearly a perfect 

 circle as is shown in diagram 2. Even if my apparatus offered a 

 possibility of pattern discrimination, my plan of control would 

 have made so variable the patterns confronting the animal that 

 they never could have served as a basis of discrimination. 



. Hunter has apparently missed one of the essential features of 

 the apparatu s which was used in my study. The dark-room 



• op. at. 



