274 The Origin and Differentiation of the Optic Vesicle 
Fic. 9. Experiment XIII,,. .The ectoderm over the right eye of a rana 
palustris embryo at the time of fusion of the neural folds was cut away and 
the caudal one-half of a somewhat older embryo grafted on so that the optic 
vesicle projected towards the celom. Embryo killed 17 days after. Section 
shows projecting from the side of the brain a large eye, which is in contact 
with the peritoneum by the retinal layer. Invagination did not occur and 
the large vesicle cavity is connected with the ventricle by a wide opening. 
x 45 diameters. 
Fic. 10. More lateral section through above eye. X 45 diameters. 
Fig. 11. Section through pigment layer of above eye. X 180 diameters. 
Fic. 12. Section through pigment layer of a normal eye. xX 180 diameters. 
Fic. 18. Experiment DL.,. Optic vesicle of embryo of rana sylvatica was 
transplanted to otic region of same embryo. Embryo killed 4 days after 
operation. In transplanting the eye it was broken into two separate pieces. 
Section through larger piece of transplanted eye which lies ventral to the 
otic vesicle. This transplanted eye shows regular invagination and begin- 
ning differentiation of the retinal layers; a small piece of brain is attached 
to it. X 90 diameters. 
Fic. 14. Experiment DL,,. Section through small deeply situated regen- 
erated eye. X 90 diameters. 
Fic. 15. Experiment DL,,. Section through part of transplanted eye 
which is entirely separate from regenerated or larger transplanted eye. x 90 
diameters. 
Fig. 16. Experiment DF,,. Embryo killed 4 days after optic vesicle 
was transplanted just anterior to otic vesicle. Section shows irregular in- 
vagination in the region of the choroidal fissure. The optic nerve pierces the 
retina in a different place than the choroidal fissure. X 100 diameters. 
Fic. 17. Experiment DL,,. Embryo killed 4 days after transplantation of 
optic vesicle into the otic region. Section through transplanted eye and lens 
showing optic nerve and part of optic stalk into which part of optic nerve 
runs. X 100 diameters. 
Fie. 18. Experiment IV,. Section through irregular transplanted eye of 
an embryo of rana palustris killed 5 days after the operation, showing differ- 
entiation of the optic stalk and irregular eye. > 100 diameters. 
Fic. 19. Experiment DL,,. Embryo killed 5 days after transplantation of 
the eye ventral to the otic vesicle. Section through its optic stalk showing 
nerve fiber. > 200 diameters. 
Fic. 20. Section showing attachment of optic stalk to eye. The nerve 
fibers pass along the optic stalk to a piece of attached brain tissue which was 
transplanted with the eye. 200 diameters. 
Fic. 21. Experiment DL,,. Embryo killed 4 days after transplantation of 
the optic vesicle into the otic region of the same embryo. Section through 
pigment layer and beginning of the optic stalk, showing position of nerve 
fibers at (0). X 200 diameters. 
Fic. 22. Section through middle of above optic stalk showing position of 
nerve fibers. 200 diameters. + 
Fic. 23. Section through attachment of above optic stalk to a piece of 
brain which was transplanted with the eye, the optic nerve is seen passing 
from the optic stalk into the brain. X 200 diameters. : 
