22
JANE Μ. OPPENHEIMER
einige andere Stellen des Keimes eine intensiv gelbe Färbung, so
dass wohl anzunehmen ist, dass das eisenhaltige Material hier zu
einem gelben Farbstofl umgearbeitet worden ist."
12
Roux (1895), as previously noted (Oppenheimer, 1955a), considered
movements of the blastomeres as tropistic, and Driesch (1894) too, also
before Vogt, and also under the influence of the theories on tropisms,
which were themselves deeply concerned with motion, built a whole and
comprehensive theory of induction on observations of selective movements of specific groups of mesenchyme cells towards a region of predilection in the embryonic ectoderm.
The modern field of investigation of morphogenetic movements opened
up by the brilliant studies of Vogt, though it has been subject to sporadic
exploration, has however been slow of complete invasion subsequent to
his time. Now that experimental studies still in progress are imputing
a high degree of developmental significance to selective migration (in
tissue culture, Grobstein, 1954, 1955; in other types of explants, Townes
and Holtfreter, 1955; and even, and especially, in the whole embryo,
Oppenheimer, 1955b), it is to be hoped that this area of investigation
will finally become more adequately exploited. Other pioneer studies
such as those of Nicholas (1945; see also a related paper by Ballard,
1955) on earlier stages of amphibian development than those investigated by Vogt open up other widening vistas which can provide entirely new perspectives for the embryologists of the future.
Certainly one reason for a half century of skirting rather than penetrating the field has been the highly elusive nature of the factors—except
those operating at the level of the cell itself—which account for the
migrations of cells in groups. One highly conspicuous exception to
what has just been remarked concerning the evasion of grappling with
the fundamental factors controlling morphogenetic movements is the
work of Holtfreter, whose article (1943a) demonstrating the integrative
12
I pursued [in the chick] the Utopian goal of earmarking the lower germ layer
and thus also all of its derivatives by the injection of dyes into the blastocoele. The
operation was carried out with a finely drawn-out glass cannula and was in itself
not completely fatal. Fine granules of carmine obtained by the precipitation of very
dilute carmine solutions, and also those of aniline blue, were retained; naturally
the goal was not attained. The behavior of the embryo with respect to granules of
so-called insoluble Berlin blue was however of interest. This dye, especially after
continued incubation of the egg, was no longer to be found; on the other hand, the
region surrounding the point of injection, which was always the most intensively
stained when this latter dye was used, and also a few other places in the embryo,
showed an intense yellow color, so that it stands to reason that the iron-containing
substance was here converted to a yellow dye.
JANE Μ. OPPENHEIMER
einige andere Stellen des Keimes eine intensiv gelbe Färbung, so
dass wohl anzunehmen ist, dass das eisenhaltige Material hier zu
einem gelben Farbstofl umgearbeitet worden ist."
12
Roux (1895), as previously noted (Oppenheimer, 1955a), considered
movements of the blastomeres as tropistic, and Driesch (1894) too, also
before Vogt, and also under the influence of the theories on tropisms,
which were themselves deeply concerned with motion, built a whole and
comprehensive theory of induction on observations of selective movements of specific groups of mesenchyme cells towards a region of predilection in the embryonic ectoderm.
The modern field of investigation of morphogenetic movements opened
up by the brilliant studies of Vogt, though it has been subject to sporadic
exploration, has however been slow of complete invasion subsequent to
his time. Now that experimental studies still in progress are imputing
a high degree of developmental significance to selective migration (in
tissue culture, Grobstein, 1954, 1955; in other types of explants, Townes
and Holtfreter, 1955; and even, and especially, in the whole embryo,
Oppenheimer, 1955b), it is to be hoped that this area of investigation
will finally become more adequately exploited. Other pioneer studies
such as those of Nicholas (1945; see also a related paper by Ballard,
1955) on earlier stages of amphibian development than those investigated by Vogt open up other widening vistas which can provide entirely new perspectives for the embryologists of the future.
Certainly one reason for a half century of skirting rather than penetrating the field has been the highly elusive nature of the factors—except
those operating at the level of the cell itself—which account for the
migrations of cells in groups. One highly conspicuous exception to
what has just been remarked concerning the evasion of grappling with
the fundamental factors controlling morphogenetic movements is the
work of Holtfreter, whose article (1943a) demonstrating the integrative
12
I pursued [in the chick] the Utopian goal of earmarking the lower germ layer
and thus also all of its derivatives by the injection of dyes into the blastocoele. The
operation was carried out with a finely drawn-out glass cannula and was in itself
not completely fatal. Fine granules of carmine obtained by the precipitation of very
dilute carmine solutions, and also those of aniline blue, were retained; naturally
the goal was not attained. The behavior of the embryo with respect to granules of
so-called insoluble Berlin blue was however of interest. This dye, especially after
continued incubation of the egg, was no longer to be found; on the other hand, the
region surrounding the point of injection, which was always the most intensively
stained when this latter dye was used, and also a few other places in the embryo,
showed an intense yellow color, so that it stands to reason that the iron-containing
substance was here converted to a yellow dye.