388
CH. D Ε VILLERS
shown in the film by Lewis and Roosen-Runge) undergoes powerful
contractions of the yolk mass and this expels the cytoplasm in the
direction of the blastodisc. Lewis considers these movements to be a
result of the propagation of contraction rings, corresponding to thickenings of the cortex by temporary gelification of the underlying cytoplasm. Their motion towards the animal pole would be the sign of an
egg polarity, of a cortical localization. Such directed movements, during
or after activation, have been observed in the eggs of other Teleosts:
Gasterosteus, Ammodytes (Thomopoulos, 1953b, 1954), Esox (Lindroth,
1946; Wülker, 1953) and Carassius (Yamamoto, 1934). In Salmo
(Wülker, 1953) and Oncorhynchus (Yamamoto, 1940) the cortex shows
rhythmical contractions and relaxations, undirected, which give to the
underlying oil drops a spiral motion. But in this case there is no evidence
that they cause an upflow of cytoplasm. These movements are accompanied by others—rotation, swinging, nutation—that concern the whole
egg (important literature on the egg movements will be found in
Wülker, 1953, and Kühl, 1939); Yamamoto (1940) thinks that they can
be connected with the variations of impedance measured by Hubbard
and Rothschild (1939). According to Yamamoto (1938,, 1940; see also
Wülker, 1953), cortical contractility only exists in eggs having a blastoderm small as compared to the yolk (excepting those of Coregonus and
Esox); they cannot therefore be considered as the general mechanism of
bipolar differentiation. The only way to prove that eggs are really
motionless, as they appear to be, would be to take motion pictures of
them (see the systematic notes on yolk movements in Wülker, 1953).
The general movements of the egg body and the polarized contraction
movements of bipolar differentiation are probably of the same nature,
but neither their mechanism nor their energy sources are known. The
ganeral movements are weakened by chloroform and by light between
440 and 540 Á (Thomopoulos, 1956). The usual anaesthetics of cytoplasmic movements such as ether, urethane, do not impede bipolar
differentiation (Devillers et al., 1953a); but it is reversibly stopped by
inhibitors of the respiratory chain such as KCN (Devillers et al., 1959),
though not by absence of 0 2 (Devillers, 1956b; Devillers et al., 1953b).
It must be noted that anaerobiosis acts quite slowly on the other
processes of development; the rapidity of bipolar differentiation thus
enables it to escape the action of anaerobiosis. This movement could
quite possibly finds its energy, therefore, in the respiratory cycle.
B. The Acquisition of Structural Co-ordinates
1. Polarity
The egg of Teleosts shows its polarity very early by nuclear migration
during the period of major growth (Arndt, 1954, 1956; Vakaet, 1955),
CH. D Ε VILLERS
shown in the film by Lewis and Roosen-Runge) undergoes powerful
contractions of the yolk mass and this expels the cytoplasm in the
direction of the blastodisc. Lewis considers these movements to be a
result of the propagation of contraction rings, corresponding to thickenings of the cortex by temporary gelification of the underlying cytoplasm. Their motion towards the animal pole would be the sign of an
egg polarity, of a cortical localization. Such directed movements, during
or after activation, have been observed in the eggs of other Teleosts:
Gasterosteus, Ammodytes (Thomopoulos, 1953b, 1954), Esox (Lindroth,
1946; Wülker, 1953) and Carassius (Yamamoto, 1934). In Salmo
(Wülker, 1953) and Oncorhynchus (Yamamoto, 1940) the cortex shows
rhythmical contractions and relaxations, undirected, which give to the
underlying oil drops a spiral motion. But in this case there is no evidence
that they cause an upflow of cytoplasm. These movements are accompanied by others—rotation, swinging, nutation—that concern the whole
egg (important literature on the egg movements will be found in
Wülker, 1953, and Kühl, 1939); Yamamoto (1940) thinks that they can
be connected with the variations of impedance measured by Hubbard
and Rothschild (1939). According to Yamamoto (1938,, 1940; see also
Wülker, 1953), cortical contractility only exists in eggs having a blastoderm small as compared to the yolk (excepting those of Coregonus and
Esox); they cannot therefore be considered as the general mechanism of
bipolar differentiation. The only way to prove that eggs are really
motionless, as they appear to be, would be to take motion pictures of
them (see the systematic notes on yolk movements in Wülker, 1953).
The general movements of the egg body and the polarized contraction
movements of bipolar differentiation are probably of the same nature,
but neither their mechanism nor their energy sources are known. The
ganeral movements are weakened by chloroform and by light between
440 and 540 Á (Thomopoulos, 1956). The usual anaesthetics of cytoplasmic movements such as ether, urethane, do not impede bipolar
differentiation (Devillers et al., 1953a); but it is reversibly stopped by
inhibitors of the respiratory chain such as KCN (Devillers et al., 1959),
though not by absence of 0 2 (Devillers, 1956b; Devillers et al., 1953b).
It must be noted that anaerobiosis acts quite slowly on the other
processes of development; the rapidity of bipolar differentiation thus
enables it to escape the action of anaerobiosis. This movement could
quite possibly finds its energy, therefore, in the respiratory cycle.
B. The Acquisition of Structural Co-ordinates
1. Polarity
The egg of Teleosts shows its polarity very early by nuclear migration
during the period of major growth (Arndt, 1954, 1956; Vakaet, 1955),