342 



the cornea — i.e. practically in contact with the facets — no pin-hole 

 images could be formed, and for that reason he did not quite 

 understand that suggestion on the part of Dr. Sj3itta. With 

 reference fco Professor Exner's experiment, described in Carpenter, 

 he thought the curious fact that the image of the R on the 

 window was reversed, whilst the image of the church beyond 

 . clearly pointed to a pin-hole effect in this photograph ; 

 and he drew attention to the analogy between this and the 

 phenomenon recorded by Max Levy, of Philadelphia, in his 

 diffraction experiments with the screens used in making half-tone 

 negate .Mr. Levy had found (see Process Work, January, 



1896, pp. 2 — 4) that the image produced by the clear spaces of 

 tin- cross-line screen of a T-shaped aperture was shown in correct 

 position before the plane of best focus and reversed in position 

 beyond this plane. It seemed quite conceivable that the effect in 

 Exner's photograph might be due to a similar cause. 



Dr. Karop said that he agreed in the main with Mr. Lewis. He 

 did not think that the compound " eye " of insects was an eye in 

 our sense of the term, but that it was a special organ, with a 

 function of which we could at present form no idea. 



.Mr. Conrady, referring to the question of difficulty of focussing, 

 -■.lid ho would remind members that they were dealing with lenses 

 of j^-q- in. in focal length, and that in such cases an object 1 in. 

 or more away would be practically at an infinite distance for such 

 a lens. He thought there was evidence to show that some insects 

 appreciated ultra-violet rays, just as certain insects were capable 

 of responding to sound-waves of very much shorter length than 

 could be appreciated by us. 



Mr. Scourfield cited the Entomostraca, where one had cases 

 ot a very simple form of compound eye which appeared to have 

 distinct lens<^. 



M r. F. P. Smith raised a point of difficulty in the acceptance 

 of the no-lens theory. The cornea of an insect eye — for example, 

 Dyticu8 — when simply stripped from a recently killed specimen, 

 exhibits the multiple-image phenomenon very beautifully. When, 

 however, the specimen is treated with caustic alkali it gradually 

 loses its power of producing the effect in question. The honey- 

 comb framework is unaltered, and therefore it is only reasonable 

 to suppose that a lens, or something akin to a lens, has been 

 distorted or actually destroyed in each of the hexagonal apertures. 



