9G 



EVOLUTION OF THE HUMAN EYE 



FIG. 22. Eye of an antelope showing the retractor bulbi or choanoid 

 muscle (C). S, sheath of Tenon's capsule external to choanoid. R, external 

 rectus. O, superior oblique. T, Tenon's capsule. 



., * > 5?- 



' * 



FIG. 23. Section through Gegenbauer's muscle from the inner surface of 



the cornea of a sheep. 



