Ectodermal 

 sphincter, ci!at< 



Base pi <. 



Canal of Schlemm 

 'in sclera) 

 Ciliary processes 

 lacking 



Scleral ossicle 

 ■art/ muscle 



■Sclera (cartilage) 

 'Choribid 



'Retina (avascular 

 cone a! droplets and with standard 

 double cones) 



Lizard 



Spectacle 



Mesodermal 

 sphincter, dilatator 



raconjunctiysl space 



Canal cf Schlemm 

 (in cornea) 



No cone oil droplets 



No epichoricidal lymph spaces 



Mesodermal Afcht^S c ' er3 (™™4 



Con us / // /y^Lhorioid 



■Retina (with 

 unique double cones) 



Snake 



Fig. 238. Diagrams of eyes of lizard and snake, to show the marked contrasts 



resulting from presumed loss during underground life and later acquisition by the 



snakes of features paralleling those present in their ancestors. The dotted arrows 



show the direction of application of force during accommodation. 



(From Walls, The Vertebrate Eye.) 



