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THE PERCEPTION OF FORM 



As we have already seen, the visual acuity of most Vertebrates 

 (with marked exceptions) is low ; in the activities of animal life 

 greater reliance is generally placed on the appreciation of differences 

 of luminosity and movement. Although on this account the eye may 

 often be a relatively poor optical instrument in the resolution of 

 imagery, that is not to say by any means that it is not biologically 

 useful ; to many Vertebrates living in an aquatic or nocturnal 

 environment or close to the ground with a restricted horizon, the 

 appreciation of luminosity and movement must be much more valuable 

 than an ability to resolve minutiae in form, nor would an eye capable 

 of recording elaborate patterns be of biological utility without a brain 

 sufficiently evolved to analyse and apjDreciate and utilize such 

 impressions. 



Apart from the ability of the brain to analyse and appreciate 



