Experimental Studies on the Development of the Eye. 437 



behind so that the new eye is to be viewed more as a re-formation 

 than a regeneration. Such a regenerated eye coming into con- 

 tact with the epidermis causes corneal clearing, the area of which 

 varies in size with that of the eye. If but a small portion of the 

 optic vesicle is cut away the regenerated eye will be of nearly 

 normal size, with a cornea in all respects normal except of slightly 

 less diameter to correspond to the smaller diameter of the eye. 



If more of the optic vesicle is cut awav a still smaller regenerated 

 eye and cornea will result. In Experiment VII361 (Fig. 4), the 

 somewhat irregular optic cup is about three-quarters of the diam- 

 eter of the normal one and the cornea about two-thirds of the 

 diameter of the normal cornea. In other respects the cornea is 

 like the normal one. The lens which is nearly as large as the normal 

 one is still adherent to the retina and fills the entire posterior cham- 

 ber of the eye. This is not an uncommon condition of the lens 

 in the regenerated eyes even as late as eighteen days after the 

 operation. 



If a still greater portion of the optic cup is cut away a regenerated 

 eye less than one-half the diameter of the normal one may develop 

 with a correspondingly small cornea. In Experiment VII3, 

 (Fig. 5), the small irregular optic cup contains a large lens which 

 fills completely the cup cavity. The endothelial layer stretches 

 over the lens and is for the most part in contact with it. The 

 cornea although but one-half the normal diameter is in other 

 respects like the normal one on the opposite side. 



Even more of the optic vesicle may be cut away than in the 

 preceding experiments, yet if the small regenerated eye remains 

 in contact with the skin a very small corneal area will develop. 



In the above experiments an incision was made around the 

 caudal part of the eye and the skin-flap with lens attached turned 

 forward. Varying amounts of the optic cup were cut away and 

 the skin-flap with the lens attached turned back into the original 

 position where it readily healed. 



In another series of experiments both lens and optic cup were 

 turned forward with the skin-flap and then varying amounts of 

 the deep portion of the eye cut away. The skin-flap with the 

 lens and remainder of the optic cup were then turned back into 

 position. The re-formed eyes vary in size according to the 

 amount left attached to the skin-flap, and the cornea in each 

 embryo also varies in size with the size of the re-formed eye. 



