162 



THE EYE IN EVOLUTION 



Figs. 142 to 144. — The Eyes of the King-crab, Limulvs polyphemus. 







Fig. 142. — The median eye. 





ONF 

 Fia. 143. — The lateral eye. 



Ch, chitinous carapace, with the iDajoilla-like thickening forming a lens, L ; 

 Ep, hypodermal epithelial cells ; ONF, optic nerve fibres ; R, retinal cells ; 

 V, continuation of the hypodermal cells to form a vitreous lamina (after 

 Lankester and Bourne). 



Fig. 144. — Section of the lateral eye. 

 Tangential section through the retina. The top ommatidium is cut perpen- 

 dicular to the longitudinal optic axis. Each retinule consists of a cluster of 

 cells (10 to 15 in number) arranged round the darkly staining, star-shaped 

 rhabdome. The left-central ommatidium was sliced obliquely and more 

 proximally and shows the body of the eccentric cell running into the axial 

 canal of the central rhabdome towards 1 o'clock (Waterman and Wiersma, 

 J. exp. ZooL). 



