CYTOGENETIC MECHANISMS IN SILKWORMS
247
plasmic radiation injuries (Astaurov, 1958c, 1961, 1963; Tultzeva and
Astaurov, 1958).
This predominantly nuclear nature of radiation injuries seems to be
intimately connected with the primary morphogenetic role of the nucleus
revealed in experiments on complete interspecific androgenesis.
Boveri's old ideas concerning the experimental analysis of nucleocytoplasmic interrelations by obtaining androgenetic organisms in interspecific crosses in complete form, i.e., by obtaining adult nucleocytoplasmic
interspecific hybrid animals, was accomplished for the first time in 1956.
This was achieved by a reciprocal combination of the cytoplasm and the
nucleus of two different species (or may be subspecies) of silkworms,
viz., a domestic B. mori L. and a wild B. mandarina Moore (Astaurov
and Ostriakova-Varshaver, 1957a-c). Although both parental species
have more or less great differences in practically all morphophysiological
characters, no indication was found of the control realized over any of
these characters by the maternal cytoplasm (Fig. 9). In this respect, the
data on interspecific androgenesis are quite similar to the very voluminous data obtained in interracial (intraspecific) androgenesis in B. mori.
Both interspecific and intraspecific androgenesis provide crucial evidence
concerning the decisive role of the cell nucleus in morphogenesis as well
as in the processes of intraspecific differentiation and speciation.
A widespread tendency exists in the scientific literature to evaluate
such clear-cut experimental results concerning the decisive role of nuclear
control in morphogenesis and divergent microevolution as particular
cases of no general importance, restricted to solitary experimental objects
such as Bombyx or Acetabularia.
One can read, for instance, in Hagemann's book on cytoplasmic inheritance (1964): "Diese Ergebnisse bedeuten nicht etwa, da bei Acetabularia und Bombyx kein plasmatisches Erbgut vorhanden ist. Sie zeigen
nur, da die Plasmotypen der jeweils combinierten Arten sich nicht
merklich unterscheiden."
The same view is expressed by Ryzhkov (1959). Jinks (1965) while
bringing forward many arguments in favor of extrachromosomal inheritance and plasmotype differences completely ignored such examples
as Acetabularia and Bombyx where no traces of autonomous and permanent (hereditary) cytoplasmic differences were discovered in several
rather remote nucleocytoplasmic combinations.
Of course, Hagemann's thesis is true; examples of nucleocytoplasmic
combinations lacking plasmotypic differences only prove that there exist
no such differences in these very combinations. So the question is: how
often is such a situation encountered in nature and how frequently is
the opposite one met?
The method of nuclear transfer opened the possibility of producing
247
plasmic radiation injuries (Astaurov, 1958c, 1961, 1963; Tultzeva and
Astaurov, 1958).
This predominantly nuclear nature of radiation injuries seems to be
intimately connected with the primary morphogenetic role of the nucleus
revealed in experiments on complete interspecific androgenesis.
Boveri's old ideas concerning the experimental analysis of nucleocytoplasmic interrelations by obtaining androgenetic organisms in interspecific crosses in complete form, i.e., by obtaining adult nucleocytoplasmic
interspecific hybrid animals, was accomplished for the first time in 1956.
This was achieved by a reciprocal combination of the cytoplasm and the
nucleus of two different species (or may be subspecies) of silkworms,
viz., a domestic B. mori L. and a wild B. mandarina Moore (Astaurov
and Ostriakova-Varshaver, 1957a-c). Although both parental species
have more or less great differences in practically all morphophysiological
characters, no indication was found of the control realized over any of
these characters by the maternal cytoplasm (Fig. 9). In this respect, the
data on interspecific androgenesis are quite similar to the very voluminous data obtained in interracial (intraspecific) androgenesis in B. mori.
Both interspecific and intraspecific androgenesis provide crucial evidence
concerning the decisive role of the cell nucleus in morphogenesis as well
as in the processes of intraspecific differentiation and speciation.
A widespread tendency exists in the scientific literature to evaluate
such clear-cut experimental results concerning the decisive role of nuclear
control in morphogenesis and divergent microevolution as particular
cases of no general importance, restricted to solitary experimental objects
such as Bombyx or Acetabularia.
One can read, for instance, in Hagemann's book on cytoplasmic inheritance (1964): "Diese Ergebnisse bedeuten nicht etwa, da bei Acetabularia und Bombyx kein plasmatisches Erbgut vorhanden ist. Sie zeigen
nur, da die Plasmotypen der jeweils combinierten Arten sich nicht
merklich unterscheiden."
The same view is expressed by Ryzhkov (1959). Jinks (1965) while
bringing forward many arguments in favor of extrachromosomal inheritance and plasmotype differences completely ignored such examples
as Acetabularia and Bombyx where no traces of autonomous and permanent (hereditary) cytoplasmic differences were discovered in several
rather remote nucleocytoplasmic combinations.
Of course, Hagemann's thesis is true; examples of nucleocytoplasmic
combinations lacking plasmotypic differences only prove that there exist
no such differences in these very combinations. So the question is: how
often is such a situation encountered in nature and how frequently is
the opposite one met?
The method of nuclear transfer opened the possibility of producing