238
LEO LEME2
islands after 5 days in vitro in cultures of the allantois taken from 4-6day-old chick embryos.
The occurrence of thrombocytes in tissue cultures (Delorenzi, 1935)
was mentioned in Section II, Β.
From the experiments mentioned above it follows that the explanted
young blastoderm develops mainly erythrocytes and histiocytes. On the
other hand, when erythrocyte-forming areas of the early chick blastoderms were grafted to the chorioallantoic membrane of older embryos,
the prospective erythrocyte-forming cells transformed into granuloblasts
after 2 to 4 days of further incubation (Dantschakoff, 1924).
B. Self-differentiation in the Yolk Sac Wall without Circulation (Anidian)
It has long been known that there are embryonated eggs in which the
embryonic body has not properly developed or is entirely absent, so that,
no blood circulation has been established, though a blastoderm with or
without an area vasculosa has developed. Where it exists the capillary
network of the vascular area is red in colour, irregular, and filled with
red blood corpuscles. The sinus terminalis is usually very distinct at
candling, thus forming the so-called lethal ring ('Blutring'). Avian
blastoderms with or without malformed embryos were called 'anidians'
by Dareste (1891). A classification of various types of avian anidian
blastoderms was proposed by Tur (1929). Autonomous growth and
differentiation of the vascular area after various experimental interventions has been reported by many authors, but nearly everybody has
been satisfied with this finding, and has made no further analyses of the
blood corpuscles contained in the vascular net.
The vascular area uninfluenced by circulation grows at a much slower
rate than in normal embryos, at first at about half the normal rate
(Grodzinski, 1934b), and diminishing further up to the 9th day of
incubation, when a contraction of the whole vascular area sets in
(Lemez and Rychter, 1958b).
Grodzinski (1933, 1934a), by refrigeration of eggs prior to incubation,
obtained blastoderms consisting of ectoderm and endoderm only, no
blood corpuscles developing in the absence of mesoderm. A particular
form of anidian was experimentally produced by Tur (1935), presumably
by stopping the spread of mesoderm after invagination through the
primitive streak : a vascular area was not present, but an accumulation
of young erythrocytes forming one giant blood island was found at the
site of the primitive streak.
The surviving vascular area represents in fact a tissue culture in ovo,
showing which cell types are capable of self-differentiation without a
circulatory system and without the scaffolding provided by developing
embryonic organs.
LEO LEME2
islands after 5 days in vitro in cultures of the allantois taken from 4-6day-old chick embryos.
The occurrence of thrombocytes in tissue cultures (Delorenzi, 1935)
was mentioned in Section II, Β.
From the experiments mentioned above it follows that the explanted
young blastoderm develops mainly erythrocytes and histiocytes. On the
other hand, when erythrocyte-forming areas of the early chick blastoderms were grafted to the chorioallantoic membrane of older embryos,
the prospective erythrocyte-forming cells transformed into granuloblasts
after 2 to 4 days of further incubation (Dantschakoff, 1924).
B. Self-differentiation in the Yolk Sac Wall without Circulation (Anidian)
It has long been known that there are embryonated eggs in which the
embryonic body has not properly developed or is entirely absent, so that,
no blood circulation has been established, though a blastoderm with or
without an area vasculosa has developed. Where it exists the capillary
network of the vascular area is red in colour, irregular, and filled with
red blood corpuscles. The sinus terminalis is usually very distinct at
candling, thus forming the so-called lethal ring ('Blutring'). Avian
blastoderms with or without malformed embryos were called 'anidians'
by Dareste (1891). A classification of various types of avian anidian
blastoderms was proposed by Tur (1929). Autonomous growth and
differentiation of the vascular area after various experimental interventions has been reported by many authors, but nearly everybody has
been satisfied with this finding, and has made no further analyses of the
blood corpuscles contained in the vascular net.
The vascular area uninfluenced by circulation grows at a much slower
rate than in normal embryos, at first at about half the normal rate
(Grodzinski, 1934b), and diminishing further up to the 9th day of
incubation, when a contraction of the whole vascular area sets in
(Lemez and Rychter, 1958b).
Grodzinski (1933, 1934a), by refrigeration of eggs prior to incubation,
obtained blastoderms consisting of ectoderm and endoderm only, no
blood corpuscles developing in the absence of mesoderm. A particular
form of anidian was experimentally produced by Tur (1935), presumably
by stopping the spread of mesoderm after invagination through the
primitive streak : a vascular area was not present, but an accumulation
of young erythrocytes forming one giant blood island was found at the
site of the primitive streak.
The surviving vascular area represents in fact a tissue culture in ovo,
showing which cell types are capable of self-differentiation without a
circulatory system and without the scaffolding provided by developing
embryonic organs.