488 SLONAKER. [Vol. XIII. 



of discrimination by sight. They will jump at any small 

 moving object, and are apparently not able to distinguish till 

 they have it in their mouths whether it is an article of food or 

 a pebble. Investigations again show the presence of an area 

 and absence of a fovea. 



In some of the reptiles, however, a marked difference in 

 power of discrimination by sight is noticed. Experiments were 

 made wholly on a small lizard (horned toad). If a dead fly 

 were put before him when he was hungry he would eye it 

 closely for a brief time, then quickly take it. His aim was 

 always certain, never missing his mark, while that of the ordi- 

 nary toad was more at random, throwing out her tongue indis- 

 criminately at moving objects. It is true the lizard was 

 attracted more by a live and moving fly than by a dead, motion- 

 less one, but he also had the power of perceiving things at 

 rest. This little creature possessed a sharp and well-defined 

 fovea. 



In general, birds' eyes are almost as perfect as man's, and 

 likewise the optic lobes are even greater in proportion to the' 

 size of the body than that of man. It is true that the bird 

 often catches flies as they buzz about, but it also inspects each 

 leaf carefully above and below for a worm or bug which may 

 be there in hiding, and which it seldom fails to recognize. The 

 hawk as it soars high in the heavens sees the snake, rat, or 

 mouse in the grass, and is frequently seen to dart and secure 

 its prey. Very acute sight is present in all birds and especially 

 in birds of prey. 



A great difference exists in the power of sight in mammals. 

 The primates possess the power of most acute vision. Many 

 of the mammals depend on smell and hearing more than on 

 sight. The dog picks his master out of the crowd by smell; so 

 does the sheep her lamb. Sight in these cases being only par- 

 tial recognition, as they are not sure until they have confirmed 

 their sight by the sense of smell. The same is true of the 

 cow, for she must smell of the strange cow when introduced into 

 the herd. The horse is cured of his fright by smelling of the 

 object which caused it. In all these cases we have a motion of 

 the ears, showing that the animal is not only using sight and 



