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GEORGE SZÉKELY
closure of the medullary plate (Harrison stage 20). Taking advantage of
a contralateral eye transplantation for rotating the anteroposterior and
dorsoventral axes separately, it was found that the functional specificity
was determined first along the anteroposterior axis. Normal vision was
observed following the separate rotation of the dorsoventral axis by
rotating the contralateral eye 180°. After a 90° rotation, when the
anteroposterior axis became dorsoventral and the dorsoventral axis
became anteroposterior, normal vision developed in the anterior and
posterior visual fields. If, however, a lure was presented in the lower or
upper visual field, the animal produced erroneous reactions which preserved the original function of the respective retinal quadrants. The
results indicated that the function of the anteroposterior axis is determined in early embryonic life, whereas retinal quadrants belonging to
the dorsoventral axis can adapt to their new positions. No attempt was
made to determine the exact age when the functional polarity of the
dorsoventral axis becomes differentiated, but a similar rotation of the
contralateral eye in an early larval stage resulted in erroneous optical
reactions in every quadrant of the visual field.
This finding corroborates Sperry's earlier (1945) prediction about the
separate differentiation of the two retinal axes and is in close analogy
with the morphological determination of other organ primordia (Harrison, 1921, 1945; Swett, 1937; Yntema, 1950) with respect to the separate
determination of axes and to the ability of the nondetermined parts to
adapt to their new location and differentiate accordingly. It has also
been shown that partially determined organ primordia can complete
their morphological development after being experimentally mutilated.
This phenomenon is generally called "regulative capacity" and shows a
type of self-differentiation by which the further development of a given
primordium is regulated more or less independently of the surroundings.
The next experiment shows that functional regulation of mutilated eye
primordia can occur under certain experimental conditions (Székely,
1957).
The eye primordium of T. vulgaris embryos was cut in half along the
dorsoventral axis in the tail-bud stage. After removal of the nasal half,
the upper and lower edge of the remaining temporal half were pressed
together to form a spherical body, and after complete healing this was
transplanted in the place of the contralateral eye of another embryo
(Fig. 1). The original temporal pole of the half eye primordium became
nasal, and the new "nasal" pole, built up out of the nondetermined dorsal
and ventral poles left behind after the surgery, became temporal. Eyes
with normal shape but of half the normal size developed from these
primordia. Visual tests showed that this nondetermined new pole dif-
GEORGE SZÉKELY
closure of the medullary plate (Harrison stage 20). Taking advantage of
a contralateral eye transplantation for rotating the anteroposterior and
dorsoventral axes separately, it was found that the functional specificity
was determined first along the anteroposterior axis. Normal vision was
observed following the separate rotation of the dorsoventral axis by
rotating the contralateral eye 180°. After a 90° rotation, when the
anteroposterior axis became dorsoventral and the dorsoventral axis
became anteroposterior, normal vision developed in the anterior and
posterior visual fields. If, however, a lure was presented in the lower or
upper visual field, the animal produced erroneous reactions which preserved the original function of the respective retinal quadrants. The
results indicated that the function of the anteroposterior axis is determined in early embryonic life, whereas retinal quadrants belonging to
the dorsoventral axis can adapt to their new positions. No attempt was
made to determine the exact age when the functional polarity of the
dorsoventral axis becomes differentiated, but a similar rotation of the
contralateral eye in an early larval stage resulted in erroneous optical
reactions in every quadrant of the visual field.
This finding corroborates Sperry's earlier (1945) prediction about the
separate differentiation of the two retinal axes and is in close analogy
with the morphological determination of other organ primordia (Harrison, 1921, 1945; Swett, 1937; Yntema, 1950) with respect to the separate
determination of axes and to the ability of the nondetermined parts to
adapt to their new location and differentiate accordingly. It has also
been shown that partially determined organ primordia can complete
their morphological development after being experimentally mutilated.
This phenomenon is generally called "regulative capacity" and shows a
type of self-differentiation by which the further development of a given
primordium is regulated more or less independently of the surroundings.
The next experiment shows that functional regulation of mutilated eye
primordia can occur under certain experimental conditions (Székely,
1957).
The eye primordium of T. vulgaris embryos was cut in half along the
dorsoventral axis in the tail-bud stage. After removal of the nasal half,
the upper and lower edge of the remaining temporal half were pressed
together to form a spherical body, and after complete healing this was
transplanted in the place of the contralateral eye of another embryo
(Fig. 1). The original temporal pole of the half eye primordium became
nasal, and the new "nasal" pole, built up out of the nondetermined dorsal
and ventral poles left behind after the surgery, became temporal. Eyes
with normal shape but of half the normal size developed from these
primordia. Visual tests showed that this nondetermined new pole dif-