II 



EYE 



139 



SCLEROTIC, CORNEA, CHOROID. These portions of the eyeball 

 are gradually diH'rrcntiati'd out of mesenchyme which becomes 

 concentrated round the primary parts of the eye. In the case of the 

 cornea the first stage in the developmental process consists in the 

 accumulation between 1ms and ectoderm of a clear jelly-like secretion 



FIG. 77. Variations in the early stages of the development of the Lens. 

 A-K, PrMfemc; K-l, >/m/o/< (after Habl, 1808); J, K Phyttomednsa (after Hudirctl. is-.".'). 



the 



continuous, and identical in character, with that which nils 

 optic cup. 



As development goes on (Knape, 1909), a thin layer of this 

 jelly-like material, about midway between the lens and the ectoderm, 

 becomes condensed to form the rudiment of Descemet's membrane. 

 Amoeboid cells from the mesenchyme round the optic cup creep 



