144 



of vision. With respect to eye-iids, all rep- 

 tiles are furnished more or less perfectly with 

 these, except serpents, which, in being destitute 

 of proper eye-lids, resemble most fishes. The 

 direction of the eye-ball is, as in most fishes, 

 commonly outwards ; but in the crocodile it is, 

 as in the star-gazer, a little upwards as well as 

 outwards, obviously for the purpose of enabling 

 the animal to see its land prey, as it floats lei- 

 surely just beneath the surface of the water. 

 Reptiles have also all of them, again excepting 

 serpents, another organ which all fishes want 

 namely, a lacrymal gland, the secretion from 

 which serves to bedew the anterior part of the eye 

 with moisture, and thus to facilitate the motions 

 of the eye-lids. Such an organ would evidently 

 have been quite superfluous in fishes, which are 

 always under water ; but it is particularly neces- 

 sary in amphibious animals, which, when on 

 land, must furnish from their own resources a 

 fluid so abundantly supplied to them when in 

 the water, from without. This gland is accor- 

 dingly of immense size in turtles ; arid the allu- 

 sion to crocodile's tears, as flowing easily arid 

 copiously, is familiar to every body. 



The eyes of birds are remarkable principally, 

 like the compound eyes of insects, for their great 

 size, the use of this being in both the same that 

 of enabling them, when on the wing, to see ob- 

 jects at a great distance. With respect to the 

 cornea and lens, they are directly opposed to 

 those of fishes ; since, while the cornea is com- 



