SIGHT — GENERAL 29 



Badgers are very largely nocturnal yet all the evidence 

 points to the probability that their eyes are not much relied 

 upon in darkness, though once again it is true that move- 

 ment is detected quickly enough. It almost seems as if 

 badgers use their eyes at night as a very general aid and that 

 sight plays a minor part in their activities. 



Cats are so often quoted as examples of mammals that can 

 "see in pitch darkness" that it seems necessary to say once 

 more that no animal can see in complete darkness. Cats have 

 good nocturnal vision and can catch mice under circum- 

 stances where a dog would be useless; but some degree of 

 light must be present for even a cat to see enough for its 

 purposes. 



Marine mammals — whales and seals — can see quite well 

 whether on land (seals) or under water (both) ; but whereas 

 it is obvious that the killer whales which are carnivorous, or 

 seals which also take prey beneath the surface, must use their 

 eyes, vision is not so important to the baleen whales which 

 feed by swimming through myriads of plankton organisms 

 with wide open and specially adapted mouths and throats. 



