43^ Warren Harmon Lewis. 



In still another series of experiments a portion of the optic 

 cup together with the lens and all of the epidermis over the eye 

 were cut away. In these experiments new epidermis soon covers 

 the remainder of the eye and from it the cornea develops, and here, 

 too, the size of the cornea varies with the size of the eye. This 

 formation of corneal from strange ectoderm will be treated more 

 fully in another section. 



The area of the corneal clearing of the epidermis over the optic 

 cup alone or over the naked lens is likewise in proportion to the 

 size of the area of contact of these organs with the skin. A large 

 optic cup may be so situated that only one small corner of it is 

 superficial and in contact with the epidermis. The size of the 

 corneal clearing is in proportion to this area of contact and not 

 in proportion to the size of the eye. 



D. Corneal Formation tvith the Optic Cup Alone and Without 



the Lens. 



In order to analyze more completely the influence of the eye 

 on corneal formation I have in the following series of experiments 

 excluded the possible influence of the lens and find that the early 

 stages of corneal formation will develop without the presence of 

 a lens or without a lens ever having formed from the skin. This 

 last point is illustrated by a single fortunate experiment (MD^) 

 on Amblystoma. A skin-flap was turned forward from over the 

 eye in the usual manner at a time when in normal embryos of 

 the same stage the skin is just beginning to show signs of thick- 

 ening for lens formation. A portion of the shallow optic cup 

 was cut out and the skin-flap replaced. The sections show that 

 for some reason the regenerated eye failed to cause lens forma- 

 tion, but nevertheless corneal formation is present (Fig. 6). 

 The optic cup is contracted and the cavity much reduced in size, 

 the pupil is small and the endothelial layer of the anterior chamber 

 reduced in area. The transparent corneal area is smaller than 

 normal and slightly thicker. 



If at a somewhat later stage after the lens has formed and 

 separated from the skin, but before there is any corneal clearing, 

 a skin-flap is turned forward and the lens with part of the cup 

 cut out, a small cornea will form over the small optic cup provided 

 the latter is close under the skin. (See Fig. 7, from Experiment 



