208
B. L. ASTAUROV
Yet a very pronounced variation in the percentage of pigmented eggs
exists even among batches laid by strictly isogeneous females taken
from parthenoclones which can be produced by thermal parthenogenesis
(Astaurov, 1940). This clearly shows that paratypical factors are also
at play here.
A quantitative variation in the capacity to undergo spontaneous
parthenogenesis runs parallel to a qualitative one: in contrast with the
uniformity and synchronous coloration (and development) of fertilized
eggs, parthenogenically developing ones exhibit a tardy, asynchronous,
and irregular pigmentation. As to the intensity and uniformity, their
coloration is but rarely comparable to the normal one. As a rule it is
pale and partial, or even patchy, only the micropylar region of the egg
surface exhibiting pigmentation. Instead of regular polygonal serosal
cells densely packed as honeycombs around the whole surface of the
egg (seen through the transparent chorion under a low-powered microscope), one sees sparse giant cells resembling stellate cells of the loose
connective tissue.
The more abnormal the development, the more atypical the pigmentation of the egg. Most of the poorly pigmented eggs succumb during long
(approximately 10 months) estivation and hibernation periods, shrinking like nonpigmented unfertilized ones. Only a small proportion of
better-pigmented eggs survive hibernation and resume spring development; in very few of them embryogenesis proceeds up to the formation
of larvae ready to hatch. Yet an overwhelming majority of these latter
die within the chorion even at this stage and only solitary larvae are
able to hatch. The elimination of the diapause by HC1 treatment can
shorten the whole span of parthenogenetic development by 2-3 weeks.
Spontaneous parthenogenesis can also be observed in nondiapause
(bivoltine) eggs of bi- and polyvoltine races which normally hatch on
the ninth to the fourteenth day after being laid (Astaurov, 1940). However, the success of parthenogenetic development seems to be much less
in bivoltine than in monovoltine hibernating eggs. Moreover, there is no
external sign of parthenogenetic development; owing to the lack of pigment formation in serosa cells, bivoltine eggs remain uncolored to the
very end of embryogenesis.
The frequency of hatching in the case of spontaneous parthenogenesis
is always very low; Lecaillon (1916, 1917c) obtained 8 larvae out of
about 26,000 eggs (or 3 X 10~
4
) ; Kawaguchi (1934a) succeeded in
obtaining 236 larvae out of about 238,000 eggs (9 X 10~
4
), while in all
my experimental series comprising about 6,422,000 eggs (partly bivoltine, partly monovoltine with and without the elimination of the diapause) 222 parthenogenetic larvae (3 X 10~
5
) were obtained (Astaurov,
1940). No wonder that some attempts to obtain complete spontaneous
B. L. ASTAUROV
Yet a very pronounced variation in the percentage of pigmented eggs
exists even among batches laid by strictly isogeneous females taken
from parthenoclones which can be produced by thermal parthenogenesis
(Astaurov, 1940). This clearly shows that paratypical factors are also
at play here.
A quantitative variation in the capacity to undergo spontaneous
parthenogenesis runs parallel to a qualitative one: in contrast with the
uniformity and synchronous coloration (and development) of fertilized
eggs, parthenogenically developing ones exhibit a tardy, asynchronous,
and irregular pigmentation. As to the intensity and uniformity, their
coloration is but rarely comparable to the normal one. As a rule it is
pale and partial, or even patchy, only the micropylar region of the egg
surface exhibiting pigmentation. Instead of regular polygonal serosal
cells densely packed as honeycombs around the whole surface of the
egg (seen through the transparent chorion under a low-powered microscope), one sees sparse giant cells resembling stellate cells of the loose
connective tissue.
The more abnormal the development, the more atypical the pigmentation of the egg. Most of the poorly pigmented eggs succumb during long
(approximately 10 months) estivation and hibernation periods, shrinking like nonpigmented unfertilized ones. Only a small proportion of
better-pigmented eggs survive hibernation and resume spring development; in very few of them embryogenesis proceeds up to the formation
of larvae ready to hatch. Yet an overwhelming majority of these latter
die within the chorion even at this stage and only solitary larvae are
able to hatch. The elimination of the diapause by HC1 treatment can
shorten the whole span of parthenogenetic development by 2-3 weeks.
Spontaneous parthenogenesis can also be observed in nondiapause
(bivoltine) eggs of bi- and polyvoltine races which normally hatch on
the ninth to the fourteenth day after being laid (Astaurov, 1940). However, the success of parthenogenetic development seems to be much less
in bivoltine than in monovoltine hibernating eggs. Moreover, there is no
external sign of parthenogenetic development; owing to the lack of pigment formation in serosa cells, bivoltine eggs remain uncolored to the
very end of embryogenesis.
The frequency of hatching in the case of spontaneous parthenogenesis
is always very low; Lecaillon (1916, 1917c) obtained 8 larvae out of
about 26,000 eggs (or 3 X 10~
4
) ; Kawaguchi (1934a) succeeded in
obtaining 236 larvae out of about 238,000 eggs (9 X 10~
4
), while in all
my experimental series comprising about 6,422,000 eggs (partly bivoltine, partly monovoltine with and without the elimination of the diapause) 222 parthenogenetic larvae (3 X 10~
5
) were obtained (Astaurov,
1940). No wonder that some attempts to obtain complete spontaneous