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have eyes very similar to those of fishes ; the 

 cornea being comparatively very flat ; and the 

 lens almost globular, while they are destitute of 

 proper eye-lids a kind of membrana nictitans 

 alone supplying their place and of a lacrymal 

 gland. In the other tribes the comparative con- 

 vexity of the cornea and lens is intermediate be- 

 tween that of these organs respectively in fishes 

 and birds ; while the motions of the iris are the 

 mean, as it were, of those of reptiles and birds : 

 in some quadrupeds, morever, as the cat, they 

 seem to be in some degree voluntary. The form 

 of the pupil is transversely oval in the pecora 

 and solidungula, and vertically oval in the Ferae ; 

 consistently with what I have already remarked 

 upon this subject. The direction of the eye-balls 

 is in most mammiferous animals outwards ; in 

 the ape however, baboon, monkey, and some 

 few others, it is, as in man, directly forwards : 

 further, in some quadrupeds, as the camel-leo- 

 pard, the eye-ball, though naturally directed out- 

 words, may be turned so far backwards as to 

 enable the animal to see distinctly behind it. 

 Like the nocturnal animals, also, of other 

 tribes, quadrupeds which prowl by night, such 

 as the lion, lynx, cat, bat, &c., have the struc- 

 ture which I have already more than once de- 

 scribed, as calculated to enable them to dis- 

 tinguish objects in comparative darkness. On 

 the other hand, where the habits of the animal 

 are such as to exclude it altogether from the 

 light, as no structure of the eye could have com- 



