248
B. L. ASTAUROV
adult nucleocytoplasmic hybrids in amphibians. They were obtained
between two subspecies of Xenopus laevis, X. I. laevis and X. I. victorianus (Gurdon, 1961), and between two subspecies of Rana nigromaculata, R. n. nigromaculata and R. n. brevipoda (Sambuichi, 1957, 1961).
The results were in favor of nuclear control over subspecific differences.
The same was found with regard to some specific differences, which
could be identified in nucleocytoplasmic hybrids obtained by means of
nuclear transfer between two good species, Xenopus laevis and Xenopus
tropicalis (Gurdon, 1962). The experiment of nuclear transfer performed
between different species of Amoeba (Danielli, 1958) are always quoted
as a good example of the permanent cytoplasmic control of at least some
of the characters, such as the dimension of the nucleus in the course of
vegetative reproduction of a "hybrid" clone. It is interesting to note in
this connection that no trace of cytoplasmic control was discovered in
recent nuclear transfer experiments in Amoebae (Judin, 1964, 1965).
C. Mosaicism and Gynandromorphism
Mosaicism and gynandromorphism are quite common phenomena in
the silkworm; there are several different kinds of mosaics in terms of
their mode of origin. Only such cases of mosaicism will be discussed here
which owe to alterations of the cytogenetic mechanism of maturation,
fertilization, and cleavage; mosaics owing to chromosomal aberrations,
mutable genes, somatic mutations, etc., will be omitted.
1. Hereditary
Mosaicism-Gynandromorphism
A really unique and wonderful instance of hereditary mosaicism in
B. mori was discovered by Katsuki and Akiyama (1927) and then thoroughly studied in a series of interesting investigations by Goldschmidt
and Katsuki (Goldschmidt and Katsuki, 1927, 1928, 1931; Katsuki,
1928, 1935).
These mostly bilateral gynandromorphs and somatic mosaics with
respect to a pair of autosomal characters A and a appear in crosses
of females taken from a particular strain when the genetic constitution
of the parent is 9 Aa X ç? aa or 9 aa X c? Aa, or $ Aa X cf Aa, i.e.,
when one or both parents are heterozygous Aa. According to the explanation proposed by Goldschmidt and Katsuki as early as 1931, there is a
recessive mutation (denoted afterwards by the symbol mo (mosaicism)
which causes the formation of two female pronuclei instead of the normal
one in the oocytes of homozygous female momo. The extra female pronucleus is formed from one of the polar body nuclei. Then either double
fertilization of both pronuclei occurs with the consequent formation of
two diploid cleavage nuclei or one of the cleavage nuclei is formed as
usual, via normal fertilization, and the second one via the fusion of two
B. L. ASTAUROV
adult nucleocytoplasmic hybrids in amphibians. They were obtained
between two subspecies of Xenopus laevis, X. I. laevis and X. I. victorianus (Gurdon, 1961), and between two subspecies of Rana nigromaculata, R. n. nigromaculata and R. n. brevipoda (Sambuichi, 1957, 1961).
The results were in favor of nuclear control over subspecific differences.
The same was found with regard to some specific differences, which
could be identified in nucleocytoplasmic hybrids obtained by means of
nuclear transfer between two good species, Xenopus laevis and Xenopus
tropicalis (Gurdon, 1962). The experiment of nuclear transfer performed
between different species of Amoeba (Danielli, 1958) are always quoted
as a good example of the permanent cytoplasmic control of at least some
of the characters, such as the dimension of the nucleus in the course of
vegetative reproduction of a "hybrid" clone. It is interesting to note in
this connection that no trace of cytoplasmic control was discovered in
recent nuclear transfer experiments in Amoebae (Judin, 1964, 1965).
C. Mosaicism and Gynandromorphism
Mosaicism and gynandromorphism are quite common phenomena in
the silkworm; there are several different kinds of mosaics in terms of
their mode of origin. Only such cases of mosaicism will be discussed here
which owe to alterations of the cytogenetic mechanism of maturation,
fertilization, and cleavage; mosaics owing to chromosomal aberrations,
mutable genes, somatic mutations, etc., will be omitted.
1. Hereditary
Mosaicism-Gynandromorphism
A really unique and wonderful instance of hereditary mosaicism in
B. mori was discovered by Katsuki and Akiyama (1927) and then thoroughly studied in a series of interesting investigations by Goldschmidt
and Katsuki (Goldschmidt and Katsuki, 1927, 1928, 1931; Katsuki,
1928, 1935).
These mostly bilateral gynandromorphs and somatic mosaics with
respect to a pair of autosomal characters A and a appear in crosses
of females taken from a particular strain when the genetic constitution
of the parent is 9 Aa X ç? aa or 9 aa X c? Aa, or $ Aa X cf Aa, i.e.,
when one or both parents are heterozygous Aa. According to the explanation proposed by Goldschmidt and Katsuki as early as 1931, there is a
recessive mutation (denoted afterwards by the symbol mo (mosaicism)
which causes the formation of two female pronuclei instead of the normal
one in the oocytes of homozygous female momo. The extra female pronucleus is formed from one of the polar body nuclei. Then either double
fertilization of both pronuclei occurs with the consequent formation of
two diploid cleavage nuclei or one of the cleavage nuclei is formed as
usual, via normal fertilization, and the second one via the fusion of two