15. E M B R Y O G E N E S I S in vitro
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primitive morphogenesis, may, by virtue of its form, consistency, and
size, act as a mechanical support.
Analogous experiments by Devillers (1947) have shown that trout
blastoderms (Salmo irideus), removed at the blastula stage, cannot
develop without yolk in Holtfreter's saline medium. The blastoderm of
the pike (Esox lucius), on the contrary, continued to differentiate into
primordial organs but their organization was anarchic; the yolk seems
to have had the same function of being a mechanical support, as in
Fundulus. However, Devillers (1949) obtained differentiation of primordial organs (chord, myotomes, brain, and placodes) in the egg of
trout by adding to the Holtfreter solution certain nutritive substances,
the most important of which was glucose. Nevertheless, in the absence
of yolk, organization remained generally anarchic.
In a further work Devillers, Colas and Richard (1957) investigated
the respective roles of deep blastomeres and of the enveloping layer in
morphogenesis. They removed and separated these two layers in
morulae, blastulae or very young gastrulae and cultivated them in a
nutritive medium containing glucose. Only the deep blastomeres ofthe
young gastrula gave rise to a few differentiations, and only in a small
number of cases: they produced chord, somites, and neural tissue. The
isolated enveloping layer produced no differentiations, but it became
stretched and folded as it does in the epibolic movement of gastrulation.
Reptiles. Embryo culture has only recently been attempted. The work
has not yet led to any important experimental research. But Tissue
Culture techniques have been suggested by several authors—who have
aimed mainly at following the development of embryos of viviparous
species outside the maternal uterus. Thus, Panigel (1956) cultivated
uterine eggs of the lizard £ootoca vivipara in a Petri dish on cotton
impregnated with 6 / i 0 00 NaCl solution. This process permitted the
development of embryos almost to the terminal stage. Raynaud
(1959a, b) used some ingenious glass receptacles: the lower half of the
embryo was immersed in a saline solution to which were added nutritive substances (albumin, chick serum, and synthetic media), while the
upper half, in contact with the air, maintained the respiration. Thus
he was able to cultivate young embryos of the blind-worm (Anguis
fragilis) from early stages until about the middle of their development,
and other embryos from the middle of gestation to about the end of
embryonic development. In such conditions the embryo feeds first of
all on its abundant yolk. The culture is not meant to substitute an
artificial milieu, but is meant to facilitate observation of, and experimentation on, a whole embryo, complete with its membranes.
A different technique was used by Bellairs (1951), and later by Lutz
and Dufaure (1960). It consists of separating the blastoderm from the
583
primitive morphogenesis, may, by virtue of its form, consistency, and
size, act as a mechanical support.
Analogous experiments by Devillers (1947) have shown that trout
blastoderms (Salmo irideus), removed at the blastula stage, cannot
develop without yolk in Holtfreter's saline medium. The blastoderm of
the pike (Esox lucius), on the contrary, continued to differentiate into
primordial organs but their organization was anarchic; the yolk seems
to have had the same function of being a mechanical support, as in
Fundulus. However, Devillers (1949) obtained differentiation of primordial organs (chord, myotomes, brain, and placodes) in the egg of
trout by adding to the Holtfreter solution certain nutritive substances,
the most important of which was glucose. Nevertheless, in the absence
of yolk, organization remained generally anarchic.
In a further work Devillers, Colas and Richard (1957) investigated
the respective roles of deep blastomeres and of the enveloping layer in
morphogenesis. They removed and separated these two layers in
morulae, blastulae or very young gastrulae and cultivated them in a
nutritive medium containing glucose. Only the deep blastomeres ofthe
young gastrula gave rise to a few differentiations, and only in a small
number of cases: they produced chord, somites, and neural tissue. The
isolated enveloping layer produced no differentiations, but it became
stretched and folded as it does in the epibolic movement of gastrulation.
Reptiles. Embryo culture has only recently been attempted. The work
has not yet led to any important experimental research. But Tissue
Culture techniques have been suggested by several authors—who have
aimed mainly at following the development of embryos of viviparous
species outside the maternal uterus. Thus, Panigel (1956) cultivated
uterine eggs of the lizard £ootoca vivipara in a Petri dish on cotton
impregnated with 6 / i 0 00 NaCl solution. This process permitted the
development of embryos almost to the terminal stage. Raynaud
(1959a, b) used some ingenious glass receptacles: the lower half of the
embryo was immersed in a saline solution to which were added nutritive substances (albumin, chick serum, and synthetic media), while the
upper half, in contact with the air, maintained the respiration. Thus
he was able to cultivate young embryos of the blind-worm (Anguis
fragilis) from early stages until about the middle of their development,
and other embryos from the middle of gestation to about the end of
embryonic development. In such conditions the embryo feeds first of
all on its abundant yolk. The culture is not meant to substitute an
artificial milieu, but is meant to facilitate observation of, and experimentation on, a whole embryo, complete with its membranes.
A different technique was used by Bellairs (1951), and later by Lutz
and Dufaure (1960). It consists of separating the blastoderm from the