Warren Harmon Lewis 



533 



eyes are deeply situated and are without lenses. In two deeply situated 

 transplanted eyes lenses are present but still attached to the ectoderm by 

 long pedicles. In the other embryo, however, the deeply situated trans- 

 planted eye has two lenses neither of which could have come from the 

 overlying ectoderm. With the exception of this last instance there is 

 no indication of the origin of a lens from the edge of the optic cup. 



Series XI. 



In the experiments of series XI the skin over the right side of the head 

 was completely torn away so as to expose the optic vesicle and structures 

 immediately about it. This was done on Rana palustris at the same 

 stage as experiments of series DF and lA^, see Figs. 1 and .2. The 

 anterior half or more of a slightly older embryo of Rana sylvatica was 

 grafted by the cut surface onto this denuded area of R. palustris. 



Exp erim en t X/^ 5 . 



In experiment XI- _, the head half of a Rana sylvatica embryo was 

 grafted onto the right side of the head of a younger Rana palustris. 

 The graft was placed with 



^^JUfj ^ .' rn ' 



Si^J^M^^''^ 



Fig. 29. Experiment XI;^. Outline 9 days after 

 operation, ab, line of junction between K. sylvatica 

 and palustris. oa, eye. X 1 diameters. 



the caudal cut surface 

 against the denuded area 

 and held in place for about 

 an hour by small pieces of 

 silver wire, after which time 

 fusion was fairly well estab- 

 lished. The optic vesicle at 

 the time of and shortly after 

 the grafting projected to- 

 wards the yolk and intest- 

 tine of Rana sylvatica. After 

 a few days, however, the 



right eye of R. palustris became visible beneath the skin on the ventral side 

 of R. sylvatica (see Fig. 29). Xine days after the operation the embrj^o 

 was killed. One ^^ortion of the irregularly invaginated optic cup is 

 superficial and not far beneath the skin. Between it and the skin is a 

 small, fairly well-formed lens, about 90 micro mm. in diameter, while 

 the normal lens on the left side is about 150 micro mm. in diameter. 

 It is impossible to determine if the lens of the transplanted eye has 

 arisen from the skin of R. sylvatica or of R. palustris, but in either case 

 it could not have come from the skin originally destined to give rise to 

 it, as that was completely torn away at a period before there is any trace 



