51 plint's nattjeal histoey. [Book XL 



colours ; and the eyes, when dried, of most of the fishes will 

 give out light in the dark, just in the same way as the trunk 

 of the oak when it has become rotten with extreme old age. 

 "We have already mentioned 3 the fact, that animals which turn, 

 not the eyes but the head, for the purpose of looking round, 

 are never known to wink. It is said, 4 too, that the chame- 

 leon is able to roll the eye-balls completely round. Crabs look 

 sideways, and have the eyes enclosed beneath a thin crust. 

 Those of craw-fish and shrimps are very hard and prominent, 

 and lie in a great measure beneath a defence of a similar 

 nature. Those animals, however, the eyes of which are hard, 

 have worse sight than those of which the eyes are formed of a 

 humid substance. It is said that if the eyes are taken away 

 from the young of serpents and of the swallow, 5 they will grow 

 again. In all insects and in animals covered with a shell, the 

 eyes move just in the same way as the ears of quadrupeds do ; 

 those among them which have a brittle 6 covering have the 

 eyes hard. All animals of this nature, as well as fishes and 

 insects, are destitute of eye-lids, and their eyes have no cover- 

 ing ; but in all there is a membrane that is transparent like 

 glass, spread over them. 



CHAP. 56. — THE HAIR OF THE EYE-LIBS ; WHAT ANIMALS AEE 

 WITHOUT THEM. ANIMALS WHICH CAN SEE ON ONE SIDE ONLY. 



Man has lashes on the eye-lids on either side ; and women 

 even make it their daily care to stain them ; 7 so ardent are they 

 in the pursuit of beauty, that they must even colour their 

 very eyes. It was with another view, however, that Nature 

 had provided the hair of the eyelids— they were to have acted, 

 so to say, as a kind of rampart for the protection of the sight, 

 and as an advanced bulwark against the approach of insects 

 or other objects which might accidentally come in their way. 

 It is not without some reason that it is said that the eye- 

 lashes 8 fall off with those persons who are too much given to 

 venereal pleasures. Of the other animals, the only ones that 

 have eyelashes are those that have hair on the rest of the 

 body as well ; but the quadrupeds have them on the upper 



3 B. viii. c. 45. 4 B. viii. c. 51. 



s s ee b. xxv. c. 50. 6 Or crustaceous covering. 



" Kohl is stili used in the east for the same purpose. 



8 Aristotle says so, Hist. Anim. B. iii. c. 10. 



