Warren Harmon Lewis 



515 



Two other embryos of the series DF, killed two days after the opera- 

 tion, show thickenings of the inner layer of the ectoderm over the re- 

 generated eyes (see Fig. 4) and also thickenings over the transplanted 

 eyes. These beginnings of lens-formation are in neither experiment so 

 far advanced as found in experiment DFgg. In another experiment, 

 DFg4, Fig. 3, the transplanted eye nearly touches the skin but no trace of 

 of lens formation is present. 



Experiment DF^^. 

 The embryo was killed two and one-quarter days after the operation. 

 The regenerated eye touches the ectoderm at which point there is a 

 thickening of the inner layer indicating the beginnings of lens-formation. 

 The transplanted eye, which is quite as large as the normal one but 

 irregular in form, lies between the regenerated eye and the otic capsule. 





Fig. 14. 



Fig. 15. 



Fig. 14. Experiment DFu. Oblique section through the transplanted eye. X 45 diameters. 

 Fig. 15. Experiment DFu. Section through the lens and edge of transplanted eye. X 175 

 diameters. 



At the point where it touches the ectoderm there is a thickening of the 

 inner layer, the beginning of lens formation, see Fig. 13. Two other 

 embryos killed at this period show the transplanted eye close to the 

 skin, but lens formation is wanting. 



Of sixteen embryos in the series DF, killed three days after the opera- 

 tion, twelve of the transplanted eyes are superficial and of these four 

 show lenses, three are still attached to the ectoderm. Three of these 

 four embryos with lenses over the transplanted eyes also show lenses 

 over the regenerated eyes, the fourth regenerated eye had not reached 

 the ectederm and is without a lens. In four of the sixteen experiments 

 the transplanted eyes are deeply situated in the mesenchyme. One and 

 only one of these possesses a lens and as this lens is still attached to 



