ORGANS OF SPECIAL SENSE. 115 



made up in mosaic ; but the remembrance of an obser- 

 vation of Leuwenhoek showed the idea to be unten- 

 able. The old Dutchman noticed that each corneule 

 (hexagonal lens of one ocellus) of a fly produced a 

 complete image of the flame of a candle, and not a 

 part of it. This introduces one of the most remark- 

 able objects that the microscope can exhibit, and which 

 is quickly made from the eye of a bee (although 

 that of a beetle is better). Cut out the cornea, 

 wash it clean inside with a camel-hair brush, plac *. 

 it in water, under a cover glass, and use the flat side 

 of the mirror and a |in. or Jin. objective. Focus 

 until all the hexagonal facets are visible. Now gently 

 draw back the objective, when, by daylight, a picture 

 of the window, with its bars, will be seen as formed 

 by each lens in the cornea. If the fingers be put into 

 the right position, their movements can be traced. I 

 have seen thus, simultaneously, in so many facets of 

 the bee's eye, many hundreds of pictures of two 

 houses and surrounding trees, which stood 140yds. 

 from the microscope. At night, if a sheet of tissue, 

 with a watch face roughly drawn on it, be placed in 

 front of the microscope lamp, the time can be seen 

 through each corneule. The picture is alike in each ; 

 but then, it must not be forgotten that the cornea is 

 flattened by the cover, so that all the lenses are 

 made to look in one direction. The solution of the 

 question of multiple vision appears to lie in the fact 

 that each ocellus presents a slightly different picture 

 from its neighbour, since its axis is directed to a 

 different point, but that parts apparently overlapping 

 are identical, and so are interpreted into a picture by 



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