144 The Animal Mind 



points to the existence of a specific visual quality in this 

 consciousness. 



The medusa Gonionemus is less active in darkness than 

 ia light, and comes to rest in darkened regions, where it 

 thus tends to collect (802). Such collections are evidently 

 not due to a definite choice on an animal's part. 



On the planarian, the general effect of light stimulation 

 is kinetic ; it comes to rest in the shaded portions of a ves- 

 sel (20, 425, 429, 317). Decapitated and hence eyeless 

 planarians respond to light, but their reactions are de- 

 layed (432) ; thus there is a certain amoimt of dependence 

 on the visual organ. 



Photokinetic effects seem to be common among insects, 

 many of which, the house fly, for example, and the mason 

 wasp (728), are active in light and sluggish in darkness. 

 These animals are naturally so much more active than Hy- 

 dra and planarians that we do not find them forming col- 

 lections in the regions where they can rest ; they seem able 

 to continue in rapid motion for long periods, and it is rather 

 a pleasurable than an uneasy activity that is suggested by 

 the aerial dances of insects in the sun. 



§ 40. The Problem of Visual Qualities: Invertebrates 



It is a well-known fact that when a human being with 

 normal vision looks at the band of spectral colors, the 

 band appears brightest to him in the region of the yellow. 

 Yellow rays, that is, produce most effect on the normal hu- 

 man retina. They are also the most intense rays in sun- 

 light. Now if a totally color-blind human being looks at 

 the spectrum, he sees it as a band of different grays, the 

 brightest gray being not in the yellow region but in the 

 yellow-green ; that is, it has been shifted towards the 



