VIII.
MORPHOGENESIS OF THE VERTEBRATE EYE
333
its development which have appeared recently are as follows: Walls
(1942), Rochon-Duvigneaud (1943), Mann (1949, 1957), Dejean, Leplat
and Hervouét (1958), Pirie and van Heyningen (1956), Polyak (1941,
1957) and Duke-Elder (1958). Experimental analysis of the development
of the eye, after the classical review by Mangold (1931), is dealt with
only in the short review by Twitty (1955); work on regeneration and
induction of the lens in amphibians is thoroughly analysed by Reyer
(1954b).
II. Appearance of the Primary Eye Rudiment
Within the Neural Plate
At the neurula stage the rudiment of the eye is in no way separated
from the rest of the neural plate from which it arises. The localization of
the material of the eye rudiment at this stage was defined by means of
vital staining in axolotls and newts; the data of different authors
(Woerdeman, 1929; Manchot, 1929; Jacobson, 1959) are in sufficiently
good agreement. They show that the material of the future eye lies at
the very anterior end of the neural plate in the form of two ovals
situated at either side of the mid-line, close to each other (Fig. 2(a)).
Within the neural plate it borders on the material of telencephalon and
diencephalon. It is underlain by the lateral prechordal mesoderm, its
relations with which undergo continuous changes due to the shifting
of the mesoderm and the rolling up of the neural plate. This localization,
however, does not agree with what develops from these areas of the
neural plate when they are isolated or transplanted. The results of this
kind of experiment depend on: (1) changes in the relations between the
eye area and the underlying mesoderm; (2) the stage of the donor
embryo; (3) the conditions under which the fragment is explanted or
where it is transplanted; (4) the size of the fragment; and (5) the animal
species employed.
Experiments on the transplantation and explantation of the anterior
area of the neural plate of the early neurula show that the eye rudiments
arise always from the anterior part of the neural plate with the neural
folds (Mikami, 1941b; Lopashov, 1945, 1960; von Woellwarth, 1952).
When the plate is separated from the fold and they are divided into
small fragments, eye rudiments arise more often from the median
J of the width of the neural plate, and from the transverse fold; the
frequency of eye formation diminishes laterad (Adelmann, 1930;
Alderman, 1935; Mangold, 1933, 1954, 1957; Hörstadius and Sellman,
1946; Gallera, 1947; Waechter, 1953; Nieuwkoop, Oikawa and Boddingius, 1958) (Fig. 2(6). When the external and internal layers of the
neural plate in Anurans are separated, the eyes arise from the latter
only (Dettlaff, 1945).
MORPHOGENESIS OF THE VERTEBRATE EYE
333
its development which have appeared recently are as follows: Walls
(1942), Rochon-Duvigneaud (1943), Mann (1949, 1957), Dejean, Leplat
and Hervouét (1958), Pirie and van Heyningen (1956), Polyak (1941,
1957) and Duke-Elder (1958). Experimental analysis of the development
of the eye, after the classical review by Mangold (1931), is dealt with
only in the short review by Twitty (1955); work on regeneration and
induction of the lens in amphibians is thoroughly analysed by Reyer
(1954b).
II. Appearance of the Primary Eye Rudiment
Within the Neural Plate
At the neurula stage the rudiment of the eye is in no way separated
from the rest of the neural plate from which it arises. The localization of
the material of the eye rudiment at this stage was defined by means of
vital staining in axolotls and newts; the data of different authors
(Woerdeman, 1929; Manchot, 1929; Jacobson, 1959) are in sufficiently
good agreement. They show that the material of the future eye lies at
the very anterior end of the neural plate in the form of two ovals
situated at either side of the mid-line, close to each other (Fig. 2(a)).
Within the neural plate it borders on the material of telencephalon and
diencephalon. It is underlain by the lateral prechordal mesoderm, its
relations with which undergo continuous changes due to the shifting
of the mesoderm and the rolling up of the neural plate. This localization,
however, does not agree with what develops from these areas of the
neural plate when they are isolated or transplanted. The results of this
kind of experiment depend on: (1) changes in the relations between the
eye area and the underlying mesoderm; (2) the stage of the donor
embryo; (3) the conditions under which the fragment is explanted or
where it is transplanted; (4) the size of the fragment; and (5) the animal
species employed.
Experiments on the transplantation and explantation of the anterior
area of the neural plate of the early neurula show that the eye rudiments
arise always from the anterior part of the neural plate with the neural
folds (Mikami, 1941b; Lopashov, 1945, 1960; von Woellwarth, 1952).
When the plate is separated from the fold and they are divided into
small fragments, eye rudiments arise more often from the median
J of the width of the neural plate, and from the transverse fold; the
frequency of eye formation diminishes laterad (Adelmann, 1930;
Alderman, 1935; Mangold, 1933, 1954, 1957; Hörstadius and Sellman,
1946; Gallera, 1947; Waechter, 1953; Nieuwkoop, Oikawa and Boddingius, 1958) (Fig. 2(6). When the external and internal layers of the
neural plate in Anurans are separated, the eyes arise from the latter
only (Dettlaff, 1945).