484 The Origin and Differentiation of the Lens 
page 97 we find the following statement relating to her results: ‘“ These 
results apparently furnish evidence in favor of the view that in a 
definite region of the ectoderm the cells are destined to form a lens, and . 
therefore they will produce such a structure even if an optic cup is 
lacking;” and on page 99: “It appears that the power of self-differen- 
tiation must be granted lens-forming cells of the ectoderm in the embryo 
of rana palustris.” King bases this view on the appearance of “ lens- 
like structures” attached to the inner layer of the ectoderm directly 
opposite the place where the lens is forming for the normal eye. On 
the side of the head where these “lens-like structures” are forming 
there is absolutely no trace of an optic cup, the latter having been killed 
by puncturing with a hot needle. The very nature of King’s operation 
makes us at once suspicious of these “ lens-like structures.” The punc- 
turing the side of the head with a hot needle is a very uncertain 
and crude mode of operation and as King says (p. 93): “ Presumably 
the operation destroyed that portion of the ectoderm that would nor- 
mally produce a lens.” In these operations, which were done on em- 
bryos somewhat younger than those used by me, it would seem to me also 
quite impossible to destroy the optic vesicle completely by puncturing 
the side of the brain with a hot needle without destroying completely 
those ectodermal cells which King supposed are predestined to differ- 
entiate into a lens. If these cells are killed then by operation, King’s 
whole argument falls to the ground. Operating on these embryos with 
a hot needle to such an extent as to completely or almost completely kill 
the optic vesicle and part of the brain is a very severe mode of procedure, 
and the after effects of such operations as King’s must be quite extensive, 
as about one-half of the embryos died during the first day. It is pos- 
sible that King may not have destroyed, in some instances, at the time 
of the operation, completely, the optic vesicle, and that the remnant 
left may have started the lens-like bud before the complete degeneration, 
disintegration, and disappearance of the eye resulted from the after 
effects of the operation. I have already called attention to abortive lens- 
formation, associated with degenerating eyes, and with a complete de- 
generation of the eye, such a condition as King found, might readily 
occur, especially when we consider what Le Cron found in amblystoma, 
namely, that the early stages of lens-development and differentiation 
are dependent on the continued influence of the optic vesicle or optic 
cup, for if the eye is removed without injury to the lens-plate or lens- 
bud, these structures soon cease to grow and differentiate; the earlier 
the eye is removed the less power the lens rudiment has of progressive 
