510 Experimental Studies on tlie Origin of the Lens in Amphibia 



rated eyes are separated from the skin by varying amounts of mesen- 

 chyme, they have lenses, three of which are still attached to the ecto- 

 derm, see Figs. 16, 21, 23 and 25. Five of the regenerated eyes are 

 deeply buried in the mesenchyme and probably were never at any time 

 in contact with the skin, see Fig. 17. Of these five, none have lenses 

 nor show any signs of lens-formation either in the ectoderm or from 

 the optic cup itself. The one experiment in which no signs of a regene- 

 rated eye occurred, shows no signs of lens-formation in the ectoderm 

 which would have given rise to a lens had the eye remained in its nor- 

 mal position. 



Fig. (j. Fig. 7. 



Fig. 6. Experiment IVi. Transverse section through the middle of the eye reg-ion. X 60 

 diameters. 



Fig. 7. Experiment IVi. Outline of tadpole 5 days after the operation. The right trans- 

 planted eye is seen in black. X 4 diameters. 



Of three embryos, killed four and one-half days after the operation, 

 in one the regenerated eye is near the ectoderm and has a large lens, 

 two are deeply buried in the mesenchyme and are without lenses. 



Experiment IV-^. 



This embryo exjDerimented on as above was killed five days after the 

 operation. There is no trace of an eye in the region from which the 

 optic vesicle was removed. Mesenchyme has filled in the space which 

 would normally have been occupied by the optic cup and lens so that 

 there is very little difference in the size of the two sides of the head (see 

 Fig- 6). 



