C Y T O G E N E T I C M E C H A N I S M S I N S I L K W O R M S
215
The viability of parthenogenetic larvae hatched from tetraploid eggs
in the course of further rearing is also much greater than after the
rudimentary parthenogenesis of diploid eggs. The reason is quite obvious:
it is the strict homozygosity of larvae in the case of automictic restoration of diploidy as contrasted with the lack of homozygozity in diploid
larvae obtained by simple reduction of the tetraploid egg. Only the
main features of spontaneous parthenogenesis in tetraploid silkworms
are mentioned here. Many interesting details concerning the genetic
constitution and sex of parthenogenetic larvae, the secondary restoration
of the tetraploid constitution (double reversion from tetraploidy to parthenogenetic diploidy and then again to tetraploidy by means of somatic
polyploidization) deserve special attention, and a special publication is
now being prepared.
B. Artificial Parthenogenesis
1. Methods of Activation
In 1886, Tichomiroff made his famous discovery of artificial parthenogenesis (1886a,b) ; he found that a treatment of unfertilized B. mori
eggs with solutions of strong acids (HC1 or H 2 S0 4 ), as well as excitation
by brushing can activate them to virgin development. Since then, many
attempts have been made to elaborate a reliable procedure which could
ensure not only rudimentary initiation of development but also its successful completion. Many physical and chemical stimulants have been
added to those found by Tichomiroff. Perhaps it would be much easier
to name physical or chemical treatments that have not been tried than
to enumerate all those that have (very often more or less successfully).
Extensive literature reviews can be found in Astaurov (1940, 1962).
For further discussion, the papers of Koltzoff (1932a,b), Bataillon and
Tchou-Su (1933), Vermel (1932, 1934), and Frolova (1935) deserve special attention. Sometimes the effectiveness of activation appeared to be
uncertain, all the more so since almost all experiments were performed
on oviposited unfertilized eggs which display some (often very high)
proportion of spontaneous parthenogenesis without any treatment (Section ΙΙΙ,Α,Ι). Yet many procedures of artificial activation proved to be
undoubtedly effective; among them the heat shock tried for the first
time also by Tichomiroff (1902) and by several other students after
him appeared to be the most effective.
2. Abortive Development in Case of Chromosome Reduction
Although the efficiency of artificial activation as expressed in the percentage of pigmented eggs frequently appeared to be quite satisfactory,
usually this success was purely quantitative. The qualitative success of
artificial parthenogenesis, i.e., the ability of activated ova to undergo
215
The viability of parthenogenetic larvae hatched from tetraploid eggs
in the course of further rearing is also much greater than after the
rudimentary parthenogenesis of diploid eggs. The reason is quite obvious:
it is the strict homozygosity of larvae in the case of automictic restoration of diploidy as contrasted with the lack of homozygozity in diploid
larvae obtained by simple reduction of the tetraploid egg. Only the
main features of spontaneous parthenogenesis in tetraploid silkworms
are mentioned here. Many interesting details concerning the genetic
constitution and sex of parthenogenetic larvae, the secondary restoration
of the tetraploid constitution (double reversion from tetraploidy to parthenogenetic diploidy and then again to tetraploidy by means of somatic
polyploidization) deserve special attention, and a special publication is
now being prepared.
B. Artificial Parthenogenesis
1. Methods of Activation
In 1886, Tichomiroff made his famous discovery of artificial parthenogenesis (1886a,b) ; he found that a treatment of unfertilized B. mori
eggs with solutions of strong acids (HC1 or H 2 S0 4 ), as well as excitation
by brushing can activate them to virgin development. Since then, many
attempts have been made to elaborate a reliable procedure which could
ensure not only rudimentary initiation of development but also its successful completion. Many physical and chemical stimulants have been
added to those found by Tichomiroff. Perhaps it would be much easier
to name physical or chemical treatments that have not been tried than
to enumerate all those that have (very often more or less successfully).
Extensive literature reviews can be found in Astaurov (1940, 1962).
For further discussion, the papers of Koltzoff (1932a,b), Bataillon and
Tchou-Su (1933), Vermel (1932, 1934), and Frolova (1935) deserve special attention. Sometimes the effectiveness of activation appeared to be
uncertain, all the more so since almost all experiments were performed
on oviposited unfertilized eggs which display some (often very high)
proportion of spontaneous parthenogenesis without any treatment (Section ΙΙΙ,Α,Ι). Yet many procedures of artificial activation proved to be
undoubtedly effective; among them the heat shock tried for the first
time also by Tichomiroff (1902) and by several other students after
him appeared to be the most effective.
2. Abortive Development in Case of Chromosome Reduction
Although the efficiency of artificial activation as expressed in the percentage of pigmented eggs frequently appeared to be quite satisfactory,
usually this success was purely quantitative. The qualitative success of
artificial parthenogenesis, i.e., the ability of activated ova to undergo