352
G. V. LOPASHOV
AND O. G.
STROEVA
with the eye (though it is at the same time evident that lenses go
through a certain amount of development after their separation from
the eye). The size of lens rudiments depends also on the size of the eye
rudiment acting on the ectoderm (Rotmann, 1942; Balinsky, 1957). All
these phenomena belong to the second phase when the eye cup and the
lens rudiment are intimately adherent to each other.
Where there is an additional contact between the lens rudiment and
either the ear vesicle, or the retina, there arises an additional fibre
nucleus of the lens (Dragomirov, 1929, 1932). This shows that the fibre
nucleus arises where an aggregation of lens rudiment cells occurs. If
the lens rudiment develops when completely enclosed in the retina, it
differentiates entirely into the nuclear part (Reyer, 1948; Lopashov,
1960). Lenses regenerating from pieces of iris in vitreous chambers
differentiate into the fibrillar part; those developing in the anterior
chamber, into lentoid vesicles; while in the pupil and at the border
between these situations a normal lens polarization occurs. When
development occurs in the vitreous chamber touching the retina, an
epithelial part arises at the place of contact (Mikami, 1941a). The action
of the differentiated retina on the development of parts of a regenerating
lens is different from that exerted at embryonic stages.
During the later phase of development which corresponds to the
period of the establishment of the blood circulation and to the detachment of the lens from the bottom of the retina and from the ectoderm,
the dependence of the lens on its connection with the eye acquires a
different character. Lenses that develop without a connection with the
eye slow down in their growth and begin to degenerate (Le Cron, 1907;
Filatov, 1934; Reyer, 1957; Becker, 1959; McKeehan, 1954), while on
transplantation into the eye cavity in Ambystoma they develop in a
typical manner (Reyer, 1957). Lens development seems then to depend
on specific conditions of diffuse nutrition produced by the eye. The lens
exerts a reverse action on the development of the rest of the eye, but of
a different character than it did earlier: (a) it tightens the pupillar orifice
and does not allow it to stretch with the growth of the eye; (b) it thus
contributes to the formation of different media in the anterior and
vitreous chambers; (c) it participates in the mutual regulation of size
with the neural parts of the eye (Harrison, 1929, 1935; Twitty, 1940,
1955) (the mechanism of this regulation is still not clear); (d) it prevents
regeneration of a new lens from the iris in newts, which does not occur
if the pupil is filled with the lens (Wachs, 1914; Mikami, 1941a; Reyer,
1950, 1954b; Stone, 1954).
How long is the lens-inducing capacity preserved in developing eyes?
How long is the capacity to develop into a lens preserved in the ectoderm (as well as in other tissues)? Proceeding from the consideration
G. V. LOPASHOV
AND O. G.
STROEVA
with the eye (though it is at the same time evident that lenses go
through a certain amount of development after their separation from
the eye). The size of lens rudiments depends also on the size of the eye
rudiment acting on the ectoderm (Rotmann, 1942; Balinsky, 1957). All
these phenomena belong to the second phase when the eye cup and the
lens rudiment are intimately adherent to each other.
Where there is an additional contact between the lens rudiment and
either the ear vesicle, or the retina, there arises an additional fibre
nucleus of the lens (Dragomirov, 1929, 1932). This shows that the fibre
nucleus arises where an aggregation of lens rudiment cells occurs. If
the lens rudiment develops when completely enclosed in the retina, it
differentiates entirely into the nuclear part (Reyer, 1948; Lopashov,
1960). Lenses regenerating from pieces of iris in vitreous chambers
differentiate into the fibrillar part; those developing in the anterior
chamber, into lentoid vesicles; while in the pupil and at the border
between these situations a normal lens polarization occurs. When
development occurs in the vitreous chamber touching the retina, an
epithelial part arises at the place of contact (Mikami, 1941a). The action
of the differentiated retina on the development of parts of a regenerating
lens is different from that exerted at embryonic stages.
During the later phase of development which corresponds to the
period of the establishment of the blood circulation and to the detachment of the lens from the bottom of the retina and from the ectoderm,
the dependence of the lens on its connection with the eye acquires a
different character. Lenses that develop without a connection with the
eye slow down in their growth and begin to degenerate (Le Cron, 1907;
Filatov, 1934; Reyer, 1957; Becker, 1959; McKeehan, 1954), while on
transplantation into the eye cavity in Ambystoma they develop in a
typical manner (Reyer, 1957). Lens development seems then to depend
on specific conditions of diffuse nutrition produced by the eye. The lens
exerts a reverse action on the development of the rest of the eye, but of
a different character than it did earlier: (a) it tightens the pupillar orifice
and does not allow it to stretch with the growth of the eye; (b) it thus
contributes to the formation of different media in the anterior and
vitreous chambers; (c) it participates in the mutual regulation of size
with the neural parts of the eye (Harrison, 1929, 1935; Twitty, 1940,
1955) (the mechanism of this regulation is still not clear); (d) it prevents
regeneration of a new lens from the iris in newts, which does not occur
if the pupil is filled with the lens (Wachs, 1914; Mikami, 1941a; Reyer,
1950, 1954b; Stone, 1954).
How long is the lens-inducing capacity preserved in developing eyes?
How long is the capacity to develop into a lens preserved in the ectoderm (as well as in other tissues)? Proceeding from the consideration