LESSON 91.] THE EYE IN INSECTS. 291 



posed surface of the eye, as in serpents ; it is colorless and transpa- 



rent. Beneath this transparent external covering, are placed the 



transparent facets, or cornieae of the several minute compound eyes, 



and beneath this lat- 



ter layer the conical, 



transparent lenses. To 



render the description 



plain, a figure (according 



to this authority) is 



given (Fig. 411). 



1311. The structure 

 of the insect eye by 

 Marcel de Serres, was 



Subsequently Superseded Structure of the eye"of Me- Miiller's views, eye of Libel- 



11 lolontha vulgaris, Straus. lula. 



by tne Statements Ol ^ Continuous layer of trans- a. Transparent cornea. 



Vm+ a fr-nay "hi a parent hexagonal corneae. &. Crystalline lens. 



but a truer hlS- 5. The con ical transparent c. Conical lens. 



torv i<5 o-ivPTi "hw T lenses. d. The pigment. 



.ory is given Dy J . c The optic filaments? con . e> The * p ^ filament 



nected to the apices of 

 the conical lensesT 



1312. He discards 



the "epidermic covering of the cornea "of Straus, which really has 

 no existence. 



1313. Beneath the cornea, Miiller found a minute double-convex 

 lens, possessing (like the crystalline lens of man and the higher ani- 

 mals) two curves; the flatter or shallower curve being placed in 

 front, and the deeper curve behind. 



1314. The bases of the conical lenses, according to Straus, are 

 perfectly flat, but Miiller found them to be convex, and that they 

 touched the greater curve of the crystalline lens, only at the centre 

 the surrounding space being filled by the pigment. 



1315. To illustrate this theory a figure is given (Fig. 412). 



LESSON XCI. 



THE EYE IN INSECTS, CONTINUED. 



1316. Miiller, however, has not exhausted all the facts in relation 

 to the structure of this important organ of sense. 



1317. Behind the horny substance of the transparent cornea, is 

 a whitish membrane, divisible into laminae, or layers, which contains 

 the crystalline lenses; with moderate care it may be detached, re- 



