354
T. A. DETTLAFF
the duration of the same periods of development (IV, E) in sturgeons
and Amphibia, could be differences in the periodicity of morphogenetic
nuclear function (Neyfakh, 1961). Experiments with radiation-induced
inactivation of the nuclei have shown that in sturgeon species the first
period of morphogenetic activity of nuclei starts in the mid-blastula and
wo
75
50
25
ν
f
C
®
22
23
24
FIG. 5. Frequency of ear vesicle formation after explantation of presumptive material
from successive developmental stages in: 1—Huso huso; 2—Acipenser stellatus; 3—Ac.
güldenstädti. (From Chulitskaya, 1962a, b.)
continues to the early gastrula. During this time the activity of the
nuclei ensures the future development of the embryo from the onset of
gastrulation up to the closure of the neural tube. During the whole
remaining period of gastrulation and the beginning of neurulation the
nuclei are inactive. Their new period of activity starts only at the end of
neurulation. At the same time in the embryos of the three anuran
species studied by Neyfakh (1961) no interruption in the morphogenetic
activity of the nuclei was found at these stages ; starting at the mid- or
T. A. DETTLAFF
the duration of the same periods of development (IV, E) in sturgeons
and Amphibia, could be differences in the periodicity of morphogenetic
nuclear function (Neyfakh, 1961). Experiments with radiation-induced
inactivation of the nuclei have shown that in sturgeon species the first
period of morphogenetic activity of nuclei starts in the mid-blastula and
wo
75
50
25
ν
f
C
®
22
23
24
FIG. 5. Frequency of ear vesicle formation after explantation of presumptive material
from successive developmental stages in: 1—Huso huso; 2—Acipenser stellatus; 3—Ac.
güldenstädti. (From Chulitskaya, 1962a, b.)
continues to the early gastrula. During this time the activity of the
nuclei ensures the future development of the embryo from the onset of
gastrulation up to the closure of the neural tube. During the whole
remaining period of gastrulation and the beginning of neurulation the
nuclei are inactive. Their new period of activity starts only at the end of
neurulation. At the same time in the embryos of the three anuran
species studied by Neyfakh (1961) no interruption in the morphogenetic
activity of the nuclei was found at these stages ; starting at the mid- or