210
B. L. ASTAUROV
1940; Efroimson and Rilova, 1936) and the males being strictly homozygous ought to be much less viable than heterozygous females. Their
preferential mortality must gradually change the sex ratio in the course
of development. Kawaguchi (1934a) who checked the sex ratio comparatively early in the larval life found a strong preponderance of males
(15 9 9 : 41 dd, or 73% dd);
the author's test in the fifth larval
instar gave a slight preponderance of females (44 $ $ : 35 d d, or
44% d d ) while sex determination in the same sample of parthenogenetic individuals in the imago stage gave a still more exaggerated
preponderance of females (26 9 9 : 15 d cf, or 37% d d )· The total sex
ratio 60 $ $ : 79 d d (56.8% d d ) based on all the experimental data
of Astaurov (1940), Kawaguchi (1934a), and Lecaillon (1916, 1917c,
1918), gives the impression of a normal distribution of sexes approaching 1 9 : 1 cf, but this should be obviously regarded as a mere casual
coincidence.
For an analysis of all the above-mentioned experimental data, only
those experiments were chosen where the initiation of parthenogenetic
development resulted not from artificial treatment but from natural
causes so that parthenogenesis in all these cases can be confidently
regarded as natural or spontaneous.
In some of these experiments unfertilized eggs were treated with
hydrochloric acid; the treatment was applied not earlier than 24 hr after
oviposition, i.e., to already activated eggs. Hence, HC1 treatment in such
cases only eliminated the diapause (artificial hatching), but did not
stimulate parthenogenesis.
Very similar data concerning "artificial" parthenogenesis in B. mori
were published in 1931 by Sato, although he claimed parthenogenesis in
his experiments to be caused by HC1 treatment. All the attempts to
develop a reliable method of complete artificial parthenogenesis in
B. mori prior to Sato's publication were unsuccessful; no wonder that
cytogenetic data concerning several scores of adult "artificially parthenogenetic" individuals have drawn sensational interest. Presently, there
is hardly any doubt that Sato dealt not with artificial but with spontaneous parthenogenesis in which HC1 treatment only eliminated the
diapause. His important and interesting data concerning the cytology of
parthenogenetic development and the genetic constitution of 74 parthenogenetic individuals (27 9 9 : 47 d d ) enriched our knowledge of
spontaneous but not of artificial parthenogenesis.
A cytological study of parthenogenetic maturation and development
especially in case of spontaneous parthenogenesis encountered serious
difficulties: the eggs of B. mori with their hard eggshell are not easy to
handle; only a small proportion of eggs fixed for an examination of the
maturation process are in a state of development, and a still smaller
B. L. ASTAUROV
1940; Efroimson and Rilova, 1936) and the males being strictly homozygous ought to be much less viable than heterozygous females. Their
preferential mortality must gradually change the sex ratio in the course
of development. Kawaguchi (1934a) who checked the sex ratio comparatively early in the larval life found a strong preponderance of males
(15 9 9 : 41 dd, or 73% dd);
the author's test in the fifth larval
instar gave a slight preponderance of females (44 $ $ : 35 d d, or
44% d d ) while sex determination in the same sample of parthenogenetic individuals in the imago stage gave a still more exaggerated
preponderance of females (26 9 9 : 15 d cf, or 37% d d )· The total sex
ratio 60 $ $ : 79 d d (56.8% d d ) based on all the experimental data
of Astaurov (1940), Kawaguchi (1934a), and Lecaillon (1916, 1917c,
1918), gives the impression of a normal distribution of sexes approaching 1 9 : 1 cf, but this should be obviously regarded as a mere casual
coincidence.
For an analysis of all the above-mentioned experimental data, only
those experiments were chosen where the initiation of parthenogenetic
development resulted not from artificial treatment but from natural
causes so that parthenogenesis in all these cases can be confidently
regarded as natural or spontaneous.
In some of these experiments unfertilized eggs were treated with
hydrochloric acid; the treatment was applied not earlier than 24 hr after
oviposition, i.e., to already activated eggs. Hence, HC1 treatment in such
cases only eliminated the diapause (artificial hatching), but did not
stimulate parthenogenesis.
Very similar data concerning "artificial" parthenogenesis in B. mori
were published in 1931 by Sato, although he claimed parthenogenesis in
his experiments to be caused by HC1 treatment. All the attempts to
develop a reliable method of complete artificial parthenogenesis in
B. mori prior to Sato's publication were unsuccessful; no wonder that
cytogenetic data concerning several scores of adult "artificially parthenogenetic" individuals have drawn sensational interest. Presently, there
is hardly any doubt that Sato dealt not with artificial but with spontaneous parthenogenesis in which HC1 treatment only eliminated the
diapause. His important and interesting data concerning the cytology of
parthenogenetic development and the genetic constitution of 74 parthenogenetic individuals (27 9 9 : 47 d d ) enriched our knowledge of
spontaneous but not of artificial parthenogenesis.
A cytological study of parthenogenetic maturation and development
especially in case of spontaneous parthenogenesis encountered serious
difficulties: the eggs of B. mori with their hard eggshell are not easy to
handle; only a small proportion of eggs fixed for an examination of the
maturation process are in a state of development, and a still smaller