VISION. 503 



ticular tribes of the first of these classes, as in the 

 Uranoscopus, where the eyes are directed imme- 

 diately upwards ; in the Ray and the Callio- 

 nymus^ where their direction is oblique ; and in 

 the Pleuronectes, where there is a. remarkable 

 want of symmetry between the right and left 

 sides of the body, and where both eyes, as well 

 as the mouth, are apparently situated on one 

 side. Among birds, it is only in the tribe of Owls, 

 which a:re nocturnal and predaceous, that we find 

 both eyes placed in front of the head. In the 

 lower quadrupeds, the eyes are situated laterally, 

 so that the optic axes form a very obtuse angle 

 with each other. As we ascend towards the 

 Quadrumana we find this angle becoming 

 smaller ; till at length the approximation of the 

 fields of view of the two eyes is such as to 

 admit of their being both directed to the same 

 object at the same time. In the human species 

 the axes of the two orbits approach nearer to 

 parallelism than in any of the other mammalia ; 

 and the fields of vision of both eyes coincide 

 nearly in their whole extent. This is probably 

 a circumstance of considerable importance with 

 regard to our acquisition of correct perceptions 

 by this sense. 



In the magnitude of the organ compared with 

 that of the body, we may occasionally observe 

 some relation to the character of the animal and 

 the nature of its pursuits. Herbivorous animals, 



