404 



ABTHBOPODA. 



behind this, in turn, the retina, consisting of cells which, at the 

 one end, bear ' rods ' (4 and 7), at the other joass into nerve fibres. 

 The retina and vitreous body, surrounded by 23igment, form a 



B 



Fig. 406. — Diagrammatic section through anterior (A) and posterior iB) eyes of Epeira 

 diademata. (After Grenacher.) The hinder eye shows the inverted retina; i, 

 lens; 2, vitreous Ijody ; 5, epidermis, outside this, chitinous layer ; 4, rhabdomes ; 

 5, retinal ceUs ; 6', capsule of eye ; 7, rhabdomes of inverted eye. 



spherical thickening sharply marked off from the rest of the epi- 

 thelium. These eyes, like those of vertebrates, must form inverted 

 images. 



In many spider eyes there is an inversion recalling that of the verte- 

 brates (flg. 406, B), the rhabdome lying beliind the nuclear portion of the 

 cell. Behind the rhabdomes comes a layer of strongly iridescent cells, the 

 tapetum lucidum. 



Fig. 407.— Head of drone bee (After Sw,ammerdam, from Hatschek.l Showing the 

 large faceted eyes and hetweeli them three ocelli. 



The compound eyes are much larger. Thev owe their name 

 ' faceted eyes ' to the fact that the cuticle over them is divided 

 into polygonal (usually hexagonal) areas or facets (fig. 407). Each 



