Spatially Determined Reactions 189 



wings produced by any other position causes them to rest only 

 in the "head-on" orientation. 



The responses of animals to different intensities of heat 

 seem not to involve a definite orientation of the body. A tem- 

 perature above the optimum produces wandering movements, 

 which cease when the animal happens to reach the proper 

 temperature (265, 268, 457). If we were to adopt the ter- 

 minology applied to light reactions, we should say that ther- 

 mopathy rather than thermotaxis is the rule. 



