■1 



220 The Animal Mind 



total image may thus be a mosaic formed of these spots 

 (Fig. ii). 



We have abeady seen that the orientations of certain 

 animals to light seem to be produced through a tendency 

 to take such a position that the two eyes shall be equally 

 illuminated. If the two visual fields are combined in the 

 case of such animals, as they are in our own binocular 

 vision, under ordinary conditions the oriented position 

 would give a field whose brightness is uniform throughout, 

 while any other position would give greater brightness 

 at one side of the field. If they are not combined, if 

 there is no binocular vision, we cannot imagine what the 

 resulting perception is. In the case of the starfish, we 

 have an animal which seems to " see " a vertical white wall 

 or dark wall that does not cast any actual shadow upon it ; 

 the starfish will direct its movements to or from such ob- 

 jects. Since the starfish has only eye-spots on the tips of 

 its arms, with no arrangements for the formation of an 

 image, and since the eye-spots are not arranged close enough 

 together so that differences of illumination in different parts 

 of a field could be represented by the different illunaination 

 of different eye-spots, we can explain the reaction to walls 

 only, as Cowles (156) does, by supposing that those eye- 

 spots and portions of the body nearest, say, a white wall, 

 are more strongly illuminated than those furthest away. 

 The response would then be one to different intensities of 

 stimulation on different parts of the body, and these dif- 

 ferences would not be seen as composing a visual field. 



That the direction from which the light comes influences 

 ants in finding their way is the opinion of Lubbock (441), 

 Turner (722 a), and Santschi (654). The first named found 

 that ants which had learned the way back to an artificial 

 nest were confused when two candles which had stood 



