LECTURE XIX. 

 THE ORIGIN OF THE EYE. 



Pro/. Oliver P. Jenkins. 



The senses and sense organs as illustrations of 

 gradual development of very complex processes ac- 

 complished hy very complex organs out of very simple 

 ones. 



General view of sense organs of vertebrates. The 

 essential elements. The accessory parts. 



Illustrated in more detail hy the human eye and 

 vision. Outline of the eye, optic nerve, and visual 

 centers. 



The Eye. Essential: Retina and optic nerve. 

 Their elements. Accessory : Choroid and iris ; scle- 

 rotic and cornea ; humors and lens ; muscles and 

 nerves ; conjunctiva and lids. Brief statement of 

 functions of each. 



Development of the eye in an individual vertebrate. 

 (Ontogeny.) 



Outline of the development of the germinal layers. 

 The formation of the neural canal. The budding out 

 of the optic vesicles, and a history of these to the 

 formation of retina and the optic nerve. Formation 

 of the accessory parts. 



Differences in development of eyes of fish, frog, 

 lizard, bird, mammal. 



