156 PHILOSOPHICAL TRANSACTIONS. [anNO 1 704. 



eye was very flat, like those in the human eye, and other animals ; whence I 

 concluded, that though the crystalline humour in fishes was spherical, yet the 

 same was made good by the flatness of the apple of the eye in the same fishes ; 

 whence one might probably conclude, that the eyes of fishes are of the same 

 contexture with other land- creatures, and consequently the effects in both are 

 the same. 



Having taken the eye out of the head of a living cod-fish, and put the tunica 

 cornea into several copper globes, or internal circles, it appeared that the pro- 

 tuberant roundness of the said tunic was equal to the segment of a circle, whose 

 diameter was 2 inches. The said eye was a little prominent out of the head, 

 like those of other animals, and though the tunics or apples make a larger circle, 

 yet they are not larger, and the axis of the crystalline humour was a little longer 

 than half an inch. Now if the crystalline humour (which I have sometimes 

 called the crystalline muscle) in our eyes, and in many other animals, consists 

 of a flattish roundness, and not perfectly spherical ; and if the diameter of the 

 circle made by the tunic of the said eyes be an inch long, the ci*ystalline hu- 

 mour in fishes being spherical, and their tunic describing a circle, whose dia- 

 meter is 2 inches, all these eyes, as before said, may have the same effect. 



After this I took a whiting, which weighed about Q ounces, and examining 

 its eye, found it described a circle of 14. inch in diameter, and the diameter 

 of its crystalline humour was very nearly 4- of an inch. When I dissected the 

 crystalline humour of a small fish, and found the innermost part no larger than 

 a large grain of sand, I observed that the fibrous particles, of which those ex- 

 ceedingly small scales were composed, consisted of as many parts as the upper- 

 most scal&s of the same humour. 



Being once asked why nature has given us eye-lids, seeing that fishes have 

 none ; I answered, that it was absolutely necessary for us, and all land-animals 

 to have eye- lids ; for if it were not so, and that the apple of our eyes was not 

 often moistened in the space of an hour, and all the foulness that might fall on 

 it washed away, our sight, or the tunica cornea, would be so clogged with filth, 

 that we should not be able to use our eyes ; besides, the tunic would otherwise 

 be parched up or shrunk with heat, and consequently we should become blind; 

 whereas, on the contrary, fishes living always in water, they want no eye-lids, 

 because the same water keeps their eyes always moist and clean. 



But I have since found that I was not entirely correct, for flounders, plaice, 

 soles, and I believe all flat fishes, can cover their eyes ; and if they could not, 

 I fancy they would lose their sight, because that sort of fish is not so nimble as 

 others in swimming, being only able to move their tails, the chief instruments 

 of speed, upwards and downwards ; wherefore these fishes in a storm do not 



