ANATOMY OF THE EYE. 347 



Perhaps this account may be followed with some 

 difficulty ; let us, therefore, take a single facet, and 

 trace it to its termination. Each facet being in 

 fact a distinct eye, we shall be able, in so doing, 

 to get a clear comprehension of the whole organ, 

 which is after all only made up of a large number 

 of these distinct eyes. Separating, then, one facet 

 from the rest, we find this single eye to consist of 

 several portions: 1. the six-sided facet; 2. the 

 cone-shaped cylinder, clear and transparent; 3. a 

 delicate fibre of nerve connected with the bottom 

 of this cone ; and, 4. the large nerve itself. The 

 diagram on the next page will make this perfectly 

 intelligible. 



But it may be asked, What of the colouring 

 matter? It exists in three places. 1. The first 

 layer surrounds the cones (2), and separates them 

 from one another, and from the nerve below 

 in part. 2. The second layer surrounds the 

 nerve fibres (3). And, 3. the last layer is at the 

 junction of the nerve fibre (3) with the nerve 

 itself (4). 



This apparently complicated mechanism well 

 deserves the reader's attention; nor should the 

 subject be quitted until it is clearly understood. 



