THE PERCEPTION OF SPACE 



687 



blue duck of New Zealand {Hymenola-tmis malacorhynchus) have frontally- 

 directed eyes and considerable binocular fields. 



The binocular fields of mammals also vary within wide limits 

 (Figs. 830-9). Some, particularly timid tj^pes, have divergent optic 

 axes and a small binocular field ; in others, particularly predators, the 

 optic axes tend towards frontal parallelism and the binocular field is 

 more extensive. The first class is exemplified by the Rodents. In 

 the rabbit there is an overlap of the circumferential uniocular fields 



Figs. 835 and 836. — Binocular Vision in Placentals. 



Fu;. 



C^oo. lilt' (Jill. 



Fig. 836.— The gorilla (Zool. Soc, London). 



In the cat frontality is required for predatory purposes (Fig. 806) ; in 

 the primate for finesse in manipulation (Fig. 839). 



