Spatially Determined Reactions 225 



to the distance at which an object produces a reaction. 

 Caterpillars, for example, are described as giving evidence of 

 seeing a slender rod extended toward them at a distance of 

 about a centimeter ; large masses they reacted to at some- 

 what greater distance (597). It is highly doubtful whether 

 this means that the simple eye of the caterpillar could give 

 a perception of two objects as differing in size if they were 

 equally distant. Myriapods, which make very little use of 

 sight and do not perceive their prey until they touch it, 

 give evidence of seeing an obstacle having a rather broad 

 surface, the size of a visiting card, at a distance of about 

 10 cm., if it is white and reflects much light, or if it is blue ; 

 but not if it is red. 



67. The Visual Perception of Form 



The second method of studying visual images tests 

 an animal's power to discriminate forms. Bumblebees 

 were thought by Forel to evince a capacity to distinguish 

 a blue circle from a blue strip of paper when they had 

 previously found honey on a blue circle, even though the 

 two had been made to exchange places. They flew first 

 to the place where the blue circle had been, but did not 

 alight upon the strip. Wasps also, according to Forel, 

 distinguished among a disk, a cross, and a band of white 

 paper, going first to the form on which they had last found 

 honey (231). Turner (726) reports the ability of the honey- 

 bee to distinguish, in the open air, among " artefacts " 

 of various forms (disks, cornucopias, and boxes), covered 

 with various patterns such as transverse and longitudinal 

 stripes, mottled surfaces, and spotted surfaces ; if the bee 

 had found honey in an artefact of a certain pattern it 

 would select that pattern from among other patterns or 

 Q 



