2O2 The Animal Mind 



pound eyes one form may be used for near and one for far 

 vision. Spiders appear to have the principal eyes adapted 

 for far vision and the auxiliary eyes for near vision, while one 

 spider, Epeira, has part of the hinder median eye adapted to 

 each (176). 



79. Some Theoretical Considerations 

 The temptation is strong to speculate upon the essential 

 nature of the conditions which make possible true space 

 perception, the simultaneous experiencing of sensations that 

 are referred to different points in space. Such speculation 

 must be of the most tentative description, yet the following 

 suggestions seem not wholly unwarranted by the facts. For 

 one thing, it looks probable that the ability to suspend im- 

 mediate reaction is essential to space perception. Can a 

 spatial complex of sensations occur in the experience of an 

 organism unless that organism is capable of receiving a number 

 of stimuli on a sensitive surface and of suspending, for a 

 brief period at least, all reaction ? Let us take as an example 

 of such a complex a visual field, within which different color 

 and brightness qualities are arranged in definite order, some 

 above, some below, some to the right, others to the left. 

 Could such a balance of tendencies to move the eye as is 

 involved in the simultaneous perception of a number of 

 elements preserving regular space relations to each other have 

 been brought about unless no single one of the tendencies were 

 irresistible? One can readily imagine an eye functioning 

 in such a way that every stimulation of it, though occasioned 

 by rays from several different directions acting simultaneously, 

 should issue at once in a resultant movement. Would not the 

 accompanying consciousness be a single resultant sensation, 

 rather than a complex of spatially ordered elements? It is 

 a good deal easier, of course, to ask than to answer such 

 questions. 



