THE EMBRYOLOGY OF THE EYE. 69 



Fig. 16. — Pig, 3I cm. long ; A and B, frontal sections 

 through inferior wall just after closure of cleft ; C, D, E, 

 optic stalk. 



Fig. 17. — Pig, d^\ cm. long ; sagittal section optic 

 nerve ; A, collection of epiblastic cells among nerve 

 fibres ; B, entrance of central vessels. 



Fig. 18. — Optic nerve, pig. A, nerve-fibres ; C, sheath. 



Fig. 19.— A and B, pig, 3 cm. long ; C, pig, 4 cm. 

 long. 



Fig. 20. — Pig ; vertical section, junction of lids ; M, 

 Meibomian glands ; S, sweat-gland. 



Fig. 2 1. — Pig, 3 cm. long, frontal section. Lach. duct: 

 A, near nostril ; B, near eye. 



