482 The Origin and Differentiation of the Lens 
place is: that something connected with the operation started progres- 
sive degenerative changes in the optic vesicle, but before they had 
become much advanced a small lens-plate and lens-bud were stimulated. 
Owing, however, to the increase in the degeneration the eye lost for the 
most part its usual influence on the developing lens, consequently the 
great retardation and apparent stoppage of the growth and differentiation 
of the later in the vesicle stage. These eyes seem to be rapidly dis- 
appearing and it is possible if one of the embryos had been killed a few 
days later the eye would have completely degenerated and disappeared, 
leaving a lens vesicle of unknown origin, and thus might have been mis- 
taken for a self-differentiating and self-originating structure. 
In another experiment (t,,) in which tissue from another embryo 
was transplanted into the otic region without disturbing in any way 
mechanically the optic region both eyes and the brain were found to be 
degenerating, and associated with each eye is a small abortive lens 
vesicle similar to the ones shown in Figs. 77, 80, 81, and 82. The 
embryo was killed 6 days after the operation. ‘The embryo, at the time 
of the operation, was of the same age as in the other experiments, con- 
sequently there is even more difference between the size and degree of 
differentiation of these two abortive lenses and normal ones of the same 
age than between those shown in Figs. 79, or 80, and 77. 
Lens-like Structures Due to Mechanical Injury of the Ectoderm. 
In many of the embryos experimented upon, especially in rana syl- 
vatica, but also in rana palustris and amblystoma, ectodermal buds pro- 
ject into the mesenchyme from places on the ectoderm liable to have 
been injured during the operation (Figs. 45, 46, 47, 48, 49, and 50). 
Such buds are found anterior to the regenerating eye, or posterior to 
it, more often, however, in the region of the otic capsule. The injury 
bud in Fig. 48 is very similar to the lens-buds of Figs. 19 and 58, and 
to the ectodermal bud in Fig. 44. The latter was probably formed at 
the place where the normal lens was pinched off from the ectoderm. 
In making the pockets beneath the ectoderm for the transplanted 
eyes, the overlying ectoderm was often injured with the needle. Also 
in transplanting the eyes small pieces of ectoderm, either from such 
wounds or from the edge of the incision, were often pushed into the 
mesenchyme. The smaller ectodermal bodies take on a solid spherical 
form, as in Fig. 51 and resemble very much the small lens-like bodies 
of Figs. 40, 41, and 42, caused by the influence of small optic vesicles 
