Warren Harmon Lewis 521 



Experiment IV^. 



The experiments of this series (IV), as we have already noted, were 

 performed on Eana palustris at a stage before there is a trace of lens 

 formation and before the preliminary adhesion between optic vesicle 

 and skin takes place (see Figs. 1 and 2). In this experiment the right 

 optic vesicle and some adjoining brain tissue were transplanted by 

 being pushed underneath the skin from the incision ah (see Fig. 1). 

 Five days after the operation the tadpole was killed. Fig. 27 shows an 

 outline of the tadpole when in xylol. The irregularly shaped black eye 

 is some distance caudal to the normal position. In the normal position 

 there is a slight depression but no trace of an eye or lens. The sec- 

 tions show that one corner of the transplanted eye lies near the skin in 

 the region of the otic capsule. The invagination is quite irregular, as 



Fig. 27. Fig. 28. 



Fig. 27. Experiment IV9. Outline of tadpole five days after the operation. Drawn in 

 xylol. The transplanted eye is seen in black. X 4 diameters. 



Fig. 28. Experiment IV9. Section through the plane 00, see Fig. 27. The irregular 

 transplanted optic cup and the small lens are seen. X 30 diameters. 



will be seen in Fig. 28. A small lens 60 micro mm. in diameter and still 

 attached to the skin by a narrow stalk lies between this superficial por- 

 tion of the optic cup and the skin. The normal lens on the left side is 

 about 130 micro mm. in diameter and farther differentiated than the 

 right one. The sections show no trace of a regenerated eye in the nor- 

 mal position on the right side nor are any changes in the ectoderm 

 indicating lens formation. A section through this region is very much 

 like that seen in Fig. 6. 



Of twenty-one embryos, killed five days after the operation, the trans- 

 planted eyes are superficial in ten and eight of these have lenses. Of 

 the eleven deeply situated transplanted eyes but one has a lens and it is 

 still connected with the ectoderm by a long narrow pedicle. In two of 

 the above experiments both the regenerated and transplanted eyes of the 

 same embryo have lenses. 

 37 



