Warren Harmon Lewis fey 
time of the operation one cannot tell the exact position of the trans- 
planted eye, but sometimes a bulge of the ectoderm indicates its position. 
After transplantation the skin flap was turned back over the stump and 
held in place by turning the embryo over onto the operated-on side. 
Great care was taken not to injure the normal lens region of the ecto- 
derm. It can easily be seen also that no ectodermal cells from this 
region were transplanted with the eye. Healing takes place rapidly, an 
hour or even less suffices for closure of the wound. 
The embryos were killed at varying ages in Zenker’s fluid embedded 
in paraffin cut into serial sections 5 to 10 » in thickness and stained in 
hematoxylin and Congo red. 
RESULTS OF HXPERIMENTS. 
The conclusive evidence of the ability of the transplanted eye in such 
experiments to stimulate lens-formation from strange ectoderm is to be 
found when such eyes are associated with lenses or lens-like structures 
that are still attached to the ectoderm of the strange region. As the 
operating season is short and uncertainty existed as to the length of time 
which must elapse after transplantation before killing the embryo in 
order to find this condition, many operations were made in order to catch, 
if possible, a few at least of the lenses still attached to the ectoderm. 
It will be found from a study of my specimens that 3 days after the 
operation is the best time to kill the embryos in order to find the lenses 
attached to the ectoderm. 
There are, fortunately, in this series a number of such lenses or lens- 
buds still attached to the ectoderm of the strange region into which the 
eye was transplanted. These offer positive proof of the ability of the 
optic vesicle to stimulate lens-formation from strange ectoderm, ecto- 
derm which under normal conditions never gives rise to a lens. Fig. 2 
shows such a lens associated with an eye transplanted caudal to the otic 
vesicle. Its origin from the inner layer of the ectoderm is better shown 
in Fig. 3 and the size and shape of the lens in Fig. 4. It is very similar 
to the normal lens vesicle shown in Fig. 5. Fig. 6 shows another more 
irregular transplanted eye lying ventral to the otic vesicle. The lens-bud 
associated with this eye is still broadly attached to the inner layer of 
the ectoderm (see Fig. 7). Fig. 8 shows another large, irregular trans- 
planted eye with a lens-bud still attached to the inner layer of the ecto- 
derm (see Fig. 9). This lens-bud is not as large nor as far differentiated 
as the normal lens vesicle (compare with Fig. 10). Fig. 12 shows an- 
other large lens-bud connected with the ectoderm by a slender pedicle 
