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in doing this my eye was taken with thofe two protuberant parts, 

 which are placed in the fore part of the Shrimp's body, and which 

 are commonly called its head, Thefe protuberances are the eyes of 

 the Shrimp, which it has a power of moving in every direction, fo 

 as to view all furrounding objedis. 



Having taken out the tunica cornea or horny coat of thefe eyes, 

 and well cleanfed the inlides of them, I found that the tunica 

 cornea in this creature was very foft and flexible, in comparifon with 

 thofe in the eyes of flies ; and when placed before the microfcope,. 

 in order to view objedl^s through them, I found that fuch objedls ap- 

 peared with much lefs dilliridnefs and brightnefs than when viewed 

 through the optical organs of a fly. The reafon of this difference 

 I took to be, that in Shrimps, and many kinds of crabs, but more 

 particularly in Shrimps, they, being always immerfed in water, do 

 not require to be hard or tough, and, therefore, when expofcd to 

 the air and becoming dry, they contradl ; infomuch that thefe eyes 

 which, in their natural flate and united to the animal's body, are of 

 a fpherical figure, when dry lofe that fpherical fhape, and from 

 being convex become concave, by contra6ling inwardly. 



I caufed a drawing to be made of one of the eyes of the Shrimp, 

 the fame fize as it appears to the naked eye, and this may be feen. 

 at Jig. 3 1 , X. Fig. 32, A B C D, fliews a great part of the Shrimp's 

 eye, as feen by the limner through the microfcope, and here may be 

 feen a number of optical organs in that fingle particle or fpot which 

 we commonly call the eye. But, as in many flies each optical or- 

 gan feems to be furrounded with a kind of border of fix fides, here, 

 in the Shrimp, each optical organ is contained in a kind of fquare. 



In the figure, that which in every optical organ is reprefented by 

 a fmall circle, is to denote a cavity or finking, but which originally 

 was of a perfedl protuberant fperical figure, until the optical organs 

 in the Shrimp, upon drjing, became contrafted. 



Fig. 33, E F G H I, exhibits another large portion of the Shrimp's 

 eye, placed in a diredl line oppofite to the fpedator. Between the 



