356
T. A. DETTLAFF
revealed differences in the manifestation of lens-forming capacity of the
lens-forming and trunk epithelium in different amphibian species.
The next important step in the study of specific differences in morphogenetic interrelations was made by Filatov (1939a, b, 1943). Being
very much interested in these problems, Filatov devoted his labour and
time to arguing the importance of comparative morphological investigations in the mechanics of development and in formulating the fundamental questions involved in work of this kind. During the period when
a large number of unconnected data on the time and factors of determination of different rudiments in different amphibian species appeared
in the literature, Filatov (1939a, b) regarded the prime problems as those
concerned with generalizations about the processes of determination in
different organogeneses and about underlying specific differences in formative interactions and the time of the determination of rudiments. On the
basis of systematic investigations Filatov showed that the formative
properties of epithelia with respect to the formation of the lenses and
balancers underwent changes in different species in parallel, and these
changes were the consequence of more general evolutionary changes in
epithelia which consisted in the different tempo of their differentiation.
Later Ginsburg, on the basis of a detailed investigation of the time of
latent differentiation of the labyrinth material in ten amphibian species
(cf. V), as well as on the basis of a comparison of data in the literature on
the time of latent differentiation of other ectoderm derivatives in these
species, has concluded that the generalization found by Filatov holds
true for different ectodermal derivatives. Ginsburg (1950b) writes that
'species specificity in the development of different ectodermal rudiments
are based on specific peculiarities of the ectoderm as a whole : more or
less earlier latent differentiation of the ectoderm into areas with steady
organogenic specificity (manifested upon transplantation in the formation of the olfactory organ, the lens, the labyrinth, the epidermis etc.,
corresponding to the origin)'. It turned out therefore that the anurans as
a whole were characterized by an earlier differentiation of the ectoderm
compared with the urodeles. Of the anurans, the earliest differentiated
occurs in Ranidae, while in urodeles, it is Ambystoma mexicanum whose
ectoderm differentiates the earliest. The ectoderm of Triturus vulgaris is
the latest to differentiate.
It turned out later that the generalization revealed for various
ectodermal derivatives held true for the derivatives of other germ layers
as well.
The processes of latent differentiation of entodermal rudiments in the
urodeles are more weakly expressed than those in the anurans at the same
developmental stages. While the liver and stomach rudiment in anuran
embryos when transplanted from the early gastrula develops according
T. A. DETTLAFF
revealed differences in the manifestation of lens-forming capacity of the
lens-forming and trunk epithelium in different amphibian species.
The next important step in the study of specific differences in morphogenetic interrelations was made by Filatov (1939a, b, 1943). Being
very much interested in these problems, Filatov devoted his labour and
time to arguing the importance of comparative morphological investigations in the mechanics of development and in formulating the fundamental questions involved in work of this kind. During the period when
a large number of unconnected data on the time and factors of determination of different rudiments in different amphibian species appeared
in the literature, Filatov (1939a, b) regarded the prime problems as those
concerned with generalizations about the processes of determination in
different organogeneses and about underlying specific differences in formative interactions and the time of the determination of rudiments. On the
basis of systematic investigations Filatov showed that the formative
properties of epithelia with respect to the formation of the lenses and
balancers underwent changes in different species in parallel, and these
changes were the consequence of more general evolutionary changes in
epithelia which consisted in the different tempo of their differentiation.
Later Ginsburg, on the basis of a detailed investigation of the time of
latent differentiation of the labyrinth material in ten amphibian species
(cf. V), as well as on the basis of a comparison of data in the literature on
the time of latent differentiation of other ectoderm derivatives in these
species, has concluded that the generalization found by Filatov holds
true for different ectodermal derivatives. Ginsburg (1950b) writes that
'species specificity in the development of different ectodermal rudiments
are based on specific peculiarities of the ectoderm as a whole : more or
less earlier latent differentiation of the ectoderm into areas with steady
organogenic specificity (manifested upon transplantation in the formation of the olfactory organ, the lens, the labyrinth, the epidermis etc.,
corresponding to the origin)'. It turned out therefore that the anurans as
a whole were characterized by an earlier differentiation of the ectoderm
compared with the urodeles. Of the anurans, the earliest differentiated
occurs in Ranidae, while in urodeles, it is Ambystoma mexicanum whose
ectoderm differentiates the earliest. The ectoderm of Triturus vulgaris is
the latest to differentiate.
It turned out later that the generalization revealed for various
ectodermal derivatives held true for the derivatives of other germ layers
as well.
The processes of latent differentiation of entodermal rudiments in the
urodeles are more weakly expressed than those in the anurans at the same
developmental stages. While the liver and stomach rudiment in anuran
embryos when transplanted from the early gastrula develops according