ORGANS OF SPECIAL SENSE 



273 



scl. C. - 



Uf.fi 



-op.ri. 



-olf. 



FIG. 159. Frontal section of the eye of an eight day chick. 



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 serrate,/ 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., Upper 

 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 



