186
R. LALLIER
The cytoplasm also contains numerous ringed lamellae, free for the most
part; a proportion of them corresponds to a typical ergastoplasm.
Ribonucleic acid may be localized in the 'heavy bodies', the vesicular
ergastoplasm and an indeterminate heavy material. The ribonucleic acid
having an indeterminate localization may be bound either to an
unknown structure or to the mitochondria. If this last possibility is
verified, it would indicate that the nature of the embryonic mitochondria
differs from that of the adult mitochondria (Pasteels et al., 1958).
Moreover, eggs contain three types of granules, staining metachromatically in vivo, rich in acid phosphatase and mucopolysaccharides. In the
centrifuged eggs, these metachromatic granules accumulate in the same
zone as the Golgi elements.
Observed with the electron microscope, the micromeres, the most
vegetative material of the sea urchin egg, show a denser and closer
reticulum than that of the mesomeres. The cytoplasm of the micromeres
also appears rich in lipids (Lehmann, 1950). According to Elbers (1959)
lithium ions exert no influence visible with the electron microscope, on
Paracentrotus
eggs if the concentration is weak enough to avoid
cytolysis. From this, Elbers concludes that the action of lithium is
limited to the cell membrane. In these experiments, the fertilized eggs
treated with lithium stop developing at the second cleavage. It would be
interesting to study the structure of fully differentiated animalized or
vegetalized embryos under the electron microscope. With regard to
the question of the permeability of the sea urchin egg to lithium, we
must point out that all the interpretations of the effects of lithium, that
we have presented so far, imply the penetration of the ions into the egg.
Moreover, Ranzi and Falkenheim (1937), by a spectroscopic method,
have detected lithium in sea urchin eggs. The problem of the penetration
of lithium ions could be efficiently studied by the autoradiographic
techniques already used by Ficq (1954) and by Dent and Sheppard
(1957) to examine the distribution of lithium in amphibian eggs.
Finally Berg et al. (1962) have studied the early gastrulae of the sea
urchin with the electron microscope. No differences in the submicroscopic
structure were observed between animal and vegetal cells. The extension
of this research to the study of animalized and vegetalized embryos is
necessary before a conclusion can be established concerning the effects
of animalization and vegetalization on cellular structures.
Changes in the physico-chemical properties of proteins have been
observed and extensively studied by Ranzi and his collaborators. Before
examining this research, we shall discuss some results concerning proteins
in normal development.
McCulloch (1952) has observed in the unfertilized eggs of Arbacia a
coarse fibrous component visible in both the polarizing and the electron
R. LALLIER
The cytoplasm also contains numerous ringed lamellae, free for the most
part; a proportion of them corresponds to a typical ergastoplasm.
Ribonucleic acid may be localized in the 'heavy bodies', the vesicular
ergastoplasm and an indeterminate heavy material. The ribonucleic acid
having an indeterminate localization may be bound either to an
unknown structure or to the mitochondria. If this last possibility is
verified, it would indicate that the nature of the embryonic mitochondria
differs from that of the adult mitochondria (Pasteels et al., 1958).
Moreover, eggs contain three types of granules, staining metachromatically in vivo, rich in acid phosphatase and mucopolysaccharides. In the
centrifuged eggs, these metachromatic granules accumulate in the same
zone as the Golgi elements.
Observed with the electron microscope, the micromeres, the most
vegetative material of the sea urchin egg, show a denser and closer
reticulum than that of the mesomeres. The cytoplasm of the micromeres
also appears rich in lipids (Lehmann, 1950). According to Elbers (1959)
lithium ions exert no influence visible with the electron microscope, on
Paracentrotus
eggs if the concentration is weak enough to avoid
cytolysis. From this, Elbers concludes that the action of lithium is
limited to the cell membrane. In these experiments, the fertilized eggs
treated with lithium stop developing at the second cleavage. It would be
interesting to study the structure of fully differentiated animalized or
vegetalized embryos under the electron microscope. With regard to
the question of the permeability of the sea urchin egg to lithium, we
must point out that all the interpretations of the effects of lithium, that
we have presented so far, imply the penetration of the ions into the egg.
Moreover, Ranzi and Falkenheim (1937), by a spectroscopic method,
have detected lithium in sea urchin eggs. The problem of the penetration
of lithium ions could be efficiently studied by the autoradiographic
techniques already used by Ficq (1954) and by Dent and Sheppard
(1957) to examine the distribution of lithium in amphibian eggs.
Finally Berg et al. (1962) have studied the early gastrulae of the sea
urchin with the electron microscope. No differences in the submicroscopic
structure were observed between animal and vegetal cells. The extension
of this research to the study of animalized and vegetalized embryos is
necessary before a conclusion can be established concerning the effects
of animalization and vegetalization on cellular structures.
Changes in the physico-chemical properties of proteins have been
observed and extensively studied by Ranzi and his collaborators. Before
examining this research, we shall discuss some results concerning proteins
in normal development.
McCulloch (1952) has observed in the unfertilized eggs of Arbacia a
coarse fibrous component visible in both the polarizing and the electron