[ 157] 



By H. M. J. Underhill. 

 Plates XIV. and XV. 



EVER since I first began to work with the microscope, when 

 I was a boy, a fly's eye has always been to me a fascinating 

 subject for study, both from the interest of its structure 

 and from the difticulty of preparing specimens. In those days my 

 ambition was to mount the part usually called the cornea, which is 

 the outer skin, consisting of lenses, in such a way as to see in it, 

 when I looked through my microscope, some hundreds of images 

 of any little thing held beneath it— one image in each lens of the 

 cornea. This I have never succeeded in doing, although I have 

 met with preparations in which I could see such an appearance ; 

 and to behold some tiny object, a watch-key for example, multi- 

 plied indefinitely, is really a very curious sight. The book whence 



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 hi sec^lon 



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Outline uf a tiy's head, showing in perspective the plane of the sections 

 into which the eyes are cut, slightly enlarged, 



I then derived my information about setting up specimens, " Hogg 

 on the Microscope,'' directs one to cut out " the eye " very 

 carefully, and with a stiff camel's hair brush to scrape out " the 

 red pigment behind it," so as to clean it for microscopical 

 examination. A\liat barbarity ! The " red pigment " in question 

 IS " the eye," and very wonderful indeed it is. Its structure can 

 only be made out when it is cut into very thin slices. This is an 

 * From 7Vie IVelcoine. 



