476 



THE EYE IN EVOLUTION 



accommodation, the pattern of the zonule becomes ntiore complex as it traverses 

 the space between the ciliary body and the lens (Fig. 622). Bundles of fibres 

 arise posteriorly from the orbicular portion of the ciliary body, run along the 

 valleys hvigging the sides of the major processes and find insertion into the lens 

 anterior to the equator. Other fibres arising more anteriorly pass backwards 

 to find insertion behind the equator, while the space between the two major 

 systems is filled with fibres arising mainly from the minor processes and running 

 perpendicularly to find insertion mainly into the posterior part of the attachment 

 zone of the lens. In the Primates, on the other hand, fibres arising posteriorly 

 in the orbicular region are inserted into the anterior lens capsule, while those 

 arising more anteriorly are inserted into the posterior capsule, the latter being 

 reinforced by perpendicular fibres arising far anteriorly ; between these two 

 main systems of fibres a space (the " canal " of Hannover, 1852) exists which is 

 traversed by a few of the fibres of the posterior system finding attachment to 

 the equator itself (Fig. 623). 



The vitreous gel is constituted as in man, the electron microscope 

 showing a system of fibrils (ox, calf, sheep, pig, rabbit — Schwarz and 

 Schuchardt, 1950 ; Schwarz, 1951). 



Figs. 624 to 626. — Types of HvALOin Vessel (Ida Mann) 



Fig. 624.— Fishes. 



Fig. 625. — Anurans. 



Fig. 626. — Mammals. 



Figs. 627 to 630. — Types of Rktinal Blood Supply in Vertebrates 

 (excluding the falciform process of Teleosts). 



Flu 327.— The Fig. 628.— The Fig. 629.— The mem- Fig. 630.— The 

 avas; AT retina. pecten or conus. brana vasculosa arteria centralis 



retinae. retinae. 



