SIGHT — GENERAL 2'] 



colours may play a big part in its existence and so the eye 

 must be capable of detecting them. 



It is a most curious thing that, in this country at least, the 

 study of mammals lags far behind the study of birds, insects, 

 and even amphibians and reptiles. There may be more than 

 one reason for this but the most likely is that mammals, being 

 far more secretive than birds, and being in many cases 

 nocturnal in their behaviour, are much more difficult to 

 observe. However, the comparatively recently formed 

 Mammal Society of the British Isles has already done much 

 to encourage more widespread and detailed work on mam- 

 malian life in which there are many aspects not fully under- 

 stood, while some still await any explanation. 



Mammals in the main are far more dependent upon their 

 marvellous senses of smell and hearing than they are on 

 sight; yet the seeing abilities of mammals present some 

 fascinating features. 



As a whole mammals are short-sighted and colour-blind. 

 Their noses and ears fulfil their long-range requirements, 

 and their visual powers are subordinate to their powers of 

 scent and hearing. Amphibians and reptiles may seem well 

 separated from the highest forms of living things, but there 

 seems to be one factor in respect of sight that links them. 

 This is that movement plays as an important a part in the 

 use of eyesight by mammals as by reptiles and amphibians. 

 The prey of mammals frequently "freeze" (stay motionless) 

 when the proximity of an enemy is detected, while the pre- 

 dator, even though it may scent its potential meal, will often 

 wait for further movement before attacking. This, of course, 

 refers only to those mammals which are carnivorous in the 

 widest sense of that word. Herbivores do not wait for the 

 breeze to move the succulent leaves of bushes or grasses, 

 because scent will tell where and what the food plants are. 

 Eyesight, in all probability, plays only a subsidiary part in 

 their feeding behaviour. 



All this does not mean that the eyes of mammals are less 

 worthy of study than the eyes of birds or fishes ; but it shows 

 that where some other sense or senses are particularly acute 

 there is less reason for great sharpness of vision. 



The degree of visual acuity may vary with different 



