268
J. H. 9. BLAXTER AND F. 0. T. HOLLJDAY
factor may be contained in the secretion of the oviduct (described in
Section VI, X). Kryzhanovsky’s observation (see Galkina, 1957)
that the eggs of Clupea pallasii seemed to be fertilized by immobile
sperm may have been due to the sperm in this instance not yet having
been activated.
The present authors and Hempel showed that when released from
the body of the female the egg of the herring had an osmotic concentration ( A 0.75) equivalent to about 12ym sea water. The process of
fertilization tends to accelerate the change to isotonicity (discussed
previously). Permeability is increased and i t is probable that the
mucopolysaccharide contents of the cortical alveoli are responsible for
drawing the outside medium through the freely permeable chorion by
some process of imbibition.
E. Parthenogenesis
Volodin (1956) described an instance of parthenogenesis in the
herring. Nearly 60% of a number of unfertilized eggs, when placed in
sea water, extruded droplets into the perivitelline space. A small
proportion of these “ activated ” eggs stopped developing after bipolar
differentiation had occurred, the remainder beginning cleavage. I n
5% of the eggs this waa abnormal, the cleavage furrows being in no
definite order and blastomeres of different sizes being produced ; these
eggs died, usually before reaching gastrulation. The remaining eggs
followed a pattern of apparently normal development, producing active
embryos. Unfortunately observations were not made aa far aa hatching.
Just what the factor is that ‘‘ activates ’’ an unfertilized egg is not
clear. It has been suggested that certain differences in osmotic pressure
between the egg and the medium may stimulate diviHion (Morgan,
1927). Unfortunately Volodin did not give the salinity of the water in
which this development took place ; apparently it could have been as
low as 4-9%,.
Galkina (1957) described parthenogenesis in C’Zupea palkz&i and
found that it occurred to a greater extent in the lower Halinitir:fi.
Development proceeded as far as hatching but thr: larvltr: wcrc ~ I P
normal.
111. THE DEVELOPING Eao
A. Embryotogy
Thc embryonic development of the herring has been studied and
described in some detail (Kupffer, 1878; Brook, 1885, 1886; Prince,
1907 ; Volodin, 1956 ; Toom, 1958) and also of Clupea pallnsii (Hamana,
J. H. 9. BLAXTER AND F. 0. T. HOLLJDAY
factor may be contained in the secretion of the oviduct (described in
Section VI, X). Kryzhanovsky’s observation (see Galkina, 1957)
that the eggs of Clupea pallasii seemed to be fertilized by immobile
sperm may have been due to the sperm in this instance not yet having
been activated.
The present authors and Hempel showed that when released from
the body of the female the egg of the herring had an osmotic concentration ( A 0.75) equivalent to about 12ym sea water. The process of
fertilization tends to accelerate the change to isotonicity (discussed
previously). Permeability is increased and i t is probable that the
mucopolysaccharide contents of the cortical alveoli are responsible for
drawing the outside medium through the freely permeable chorion by
some process of imbibition.
E. Parthenogenesis
Volodin (1956) described an instance of parthenogenesis in the
herring. Nearly 60% of a number of unfertilized eggs, when placed in
sea water, extruded droplets into the perivitelline space. A small
proportion of these “ activated ” eggs stopped developing after bipolar
differentiation had occurred, the remainder beginning cleavage. I n
5% of the eggs this waa abnormal, the cleavage furrows being in no
definite order and blastomeres of different sizes being produced ; these
eggs died, usually before reaching gastrulation. The remaining eggs
followed a pattern of apparently normal development, producing active
embryos. Unfortunately observations were not made aa far aa hatching.
Just what the factor is that ‘‘ activates ’’ an unfertilized egg is not
clear. It has been suggested that certain differences in osmotic pressure
between the egg and the medium may stimulate diviHion (Morgan,
1927). Unfortunately Volodin did not give the salinity of the water in
which this development took place ; apparently it could have been as
low as 4-9%,.
Galkina (1957) described parthenogenesis in C’Zupea palkz&i and
found that it occurred to a greater extent in the lower Halinitir:fi.
Development proceeded as far as hatching but thr: larvltr: wcrc ~ I P
normal.
111. THE DEVELOPING Eao
A. Embryotogy
Thc embryonic development of the herring has been studied and
described in some detail (Kupffer, 1878; Brook, 1885, 1886; Prince,
1907 ; Volodin, 1956 ; Toom, 1958) and also of Clupea pallnsii (Hamana,