132 Discoveries of Muller and others in the 



^ presents the 



^' '^fs^ //_^ - -^ common cor- 



the aggregated 

 mass of simple eyes : a, the vitreous bodies ; b, the filaments 

 of the optic nerve ; c, the trunk of this nerve ; d, the depres- 

 sions in the vitreous bodies for the reception of the lenses. 



In a large species of Zulus, Professor Miiller counted about 

 forty aggregated simple eyes on each side. Here also the 

 hard, transparent, amber-coloured, and nearly globular lenses 

 were fixed in depressions in the under surface of the common 

 cornea ; and the other parts appeared to be similar to those 

 in the Cymothoa. 



The vision of these animals cannot possibly be very power- 

 ful, nor extend beyond the nearest objects ; for the different 

 rays from distant objects must simultaneously affect all the 

 simple eyes aggregated together, to the complete destruction 

 of all specification of form. Those objects immediately before 

 the eyes can alone be distinguished from each other by means 

 of this structure of the organs of vision, which is indeed only 

 adapted to the Myri^podes, Onisci, and a few other kinds of 

 wingless animals, some of which live in the ground, some 

 under stones, and some even as parasites of fishes. 



Vision of Spiders, Sco7'pions, Sfc., and of Insects provided with 

 Simple Eyes or Stemmata, 



It appears from the details given, that the simple eyes of 

 the spiders, scorpions, and insects resemble those of fishes 

 in their structure; especially in the crystalline lens being 

 rounded, separated from the vitreous body, and brought close 

 to the cornea. But, in the stemmata of the articulated ani- 

 mals, the anterior chamber of the eye is completely wanting ; 

 the iris, whose internal margin in fishes embraces the lens, is 

 reduced in the Articulata to a zone of the choroid pigment on 

 the anterior surface of the vitreous body, and the lens is no 

 longer embedded in the vitreous humour, but merely in con- 

 tact with its anterior and convex surface. The space com- 

 prised between the lens, the cornea, and the front of the 

 vitreous body, is probably filled, in the living state, with some 

 peculiar fluid. Whatever this may be, the degree of refraction 



