ORGANS OF SPECIAL SENSE 



273 



Fig. 159. — Frontal section of the eye of an eight day chick. Shrinking in 

 the process of preparation has caused a separation between the retinal and 



pigment layers. -i n-i- 



ant ch., Anterior chamber of the eye. ch., Choroid coat cil., Ciliary 

 processes Corn., Cornea. 1. e. 1., Lower eyelid, n. m., Nictitating mem- 

 brane, olf.. Olfactory sac. op. n., Optic nerve, o. s Ora serrata. p 

 Pigment layer of the optic cup. post, ch., Posterior chamber of the eye. 

 ret Retina scl., Sclerotic coat. scl. C, Sclerotic cartilage, u. e. 1., Lpper 

 eyelid. 



thinner than in the ciliary region. The mesenchyme overlying 

 the iris early becomes condensed to form the stroma of the iris; 

 the epithelia form the uvea of the developed iris (Fig. 159). 

 The muscles of the iris (sphincter pupillae) are stated by 



