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they descend, as into the inverted fingers of a 

 glove. Organs of this kind may serve, indeed, 

 to distinguish between light and darkness ; but 

 it is impossible that they can convey any im- 

 pression of distinct images of objects, since they 

 have not the conditions necessary to produce 

 such refractions of the rays of light as are essen- 

 tial to this end. Among the few animals of this 

 description, which are provided with proper eyes, 

 is the cuttle, in which those organs are very 

 large and prominent. They consist essentially 

 of a dense opake globular membrane the sclero- 

 tic coat filled with a transparent fluid, envelo- 

 ping a small lens, and smeared on its concave 

 side with a black pigment, the use of which is to 

 absorb the superfluous rays of light, and immedi- 

 ately under which lies the retina or expansion of 

 the optic nerve. This membrane is perforated 

 anteriorly by a kidney-shaped pupil, through 

 which the rays of light are transmitted to the re- 

 tina ; and over the whole is extended a second 

 membrane, so folded on itself, as to constitute 

 a kind of eyelids. 



Similar to the stemmata of some worms are 

 what are called the simple eyes of insects ; and 

 such alone are found in the spider and scorpion : 

 they seem to be organs rather of touch than of 

 sight, although they have been presumed by 

 Blumenbach to serve to distinguish near objects. 

 Very different from these are the so called com- 

 pound eyes of insects, such as are met with, with- 

 out any rimple eyes, in the beetle and butterfly ; 



