INTRODUCTION 19 



in the various classes of mammals in accordance with their 

 environments. 



The herbivorous terrestrial mammals, whose safetv and 



t/ 



survival depend upon their swiftness of flight from danger, 

 such as some of the Rodentia and the Ungulata, require 

 sight, smell and hearing so developed as to enable them to 

 detect quickly the approach of danger over a wide area. 

 They grasp their food directly with their mouths, finding 

 that which is suitable more bv smell and bv the touch of 



t, t/ 



their acutely sensitive snouts than by sight. Their visual 

 organs must, therefore, be adapted for the widest possible 

 range of circumferential vision, sufficiently acute over a wide 

 area to enable them rapidly to detect any moving object 

 -such vision as is aptly termed 'panoramic vision," the 

 highest perfection of which may be described as vision which 

 enables an animal to see in its entire circumference at one 

 and the same time. They also require, to protect them- 

 selves from the evils which prowl by night as well as by 

 day, a capacity for seeing in dim as well as in bright light. 

 The terrestrial carnivorous animals, with their powerful 

 development of tooth and claw, require for their sustenance 

 and survival smell and sight, which will enable them to 

 track their prey and pounce accurately upon it when within 

 a suitable distance. They grasp their food with their mouths, 

 steadying it with their front paws while tearing it to pieces 

 with their teeth. Their visual organs must, therefore, be 

 so adapted that they can concentrate the sight of both eyes 

 on their victims at the distance from which they spring, 

 and follow quickly any movements such victims may make 

 in their endeavors to escape. For these purposes binocular 

 vision is more essential than panoramic vision. As the 

 animals upon which these Carnivora prey are comparatively 

 large, accurate vision for fine detail is not requisite. Good 



