ANIMALIZATION AND VEGETALIZATION
175
The data concerning the cells of various organisms indicate that the
enzymes of the second group are localized in the mitochondria. From
these data, Gustafson and Hasselberg inferred that in the sea urchin
embryos, these enzymes may also be mitochondrial. Gustafson and
Hasselberg (1951) concluded that embryonic differentiation includes the
elaboration of mitochondria possibly by inhibiting the development of
their precursors. Lallier (1950), as a result of the study of the utilization
of intermediate substrates of carbohydrate catabolism in the amphibian
eggs, had already concluded that lithium ions disturb the functions of
the cytoplasmic inclusions responsible for the tricarboxylic acid cycle,
i.e., the mitochondria. These results emphasize the function of mitochondria in the differentiation of eggs. Some difficulties arise, however,
from the behaviour of certain enzymes. Thus, while catalase and cytochrome oxidase are typically mitochondrial enzymes, their activity
decreases at the late blastula stage, synchronously with the rise in
activity of the mitochondrial enzymes. To explain this decrease of the
enzymatic activity, Deutsch and Gustafson (1952) have suggested the
formation of an inhibitor or the absorption of the enzyme at the intercellular surface. Alkaline phosphatase presents another problem. The
activity of this enzyme increases at the beginning of gastrulation like
the enzymes of the second group; nevertheless, in contrast to the
enzymes of the second group, the rise in activity of alkaline phosphatase
is not inhibited by lithium (Gustafson and Hasselberg, 1950).
Finally we must note that the mitochondrial distribution of enzymes
in the sea urchin egg is inferred from analogy with the observations
made on various tissues of vertebrates. As was pointed out by Brächet
(1960) the distribution of the enzymes in the sea urchin egg may differ
from that in other tissues. A direct study of the distribution of enzymes
in the sea urchin egg would remove this objection. We should also
remember that the ergastoplasm certainly plays an important role during
the differentiation of the egg. Ribosomal particles, a constituent of
ergastoplasm, are the sites of much if not all protein synthesis (Zamecnik,
1960). In the ultra-centrifugeable cytoplasmic particles of amphibian
eggs, the distribution of ribonucleic acid is altered by lithium ions
(Lallier, 1950,1954). Gustafson and Lenicque (1952,1955) have examined
the changes in the number and distribution of mitochondria in the
normal, vegetalized, and animalized sea urchin embryos. The counting
of the mitochondria is done in situ in whole embryos compressed under a
cover-slip. The mitochondria are counted in situ by the aid of a phasecontrast microscope or after vital staining with Nile blue sulphate.
During segmentation, the increase in the number of mitochondria
follows an S-shaped curve. This curve closely resembles the one observed
when measuring the increase of oxygen consumption during the same
175
The data concerning the cells of various organisms indicate that the
enzymes of the second group are localized in the mitochondria. From
these data, Gustafson and Hasselberg inferred that in the sea urchin
embryos, these enzymes may also be mitochondrial. Gustafson and
Hasselberg (1951) concluded that embryonic differentiation includes the
elaboration of mitochondria possibly by inhibiting the development of
their precursors. Lallier (1950), as a result of the study of the utilization
of intermediate substrates of carbohydrate catabolism in the amphibian
eggs, had already concluded that lithium ions disturb the functions of
the cytoplasmic inclusions responsible for the tricarboxylic acid cycle,
i.e., the mitochondria. These results emphasize the function of mitochondria in the differentiation of eggs. Some difficulties arise, however,
from the behaviour of certain enzymes. Thus, while catalase and cytochrome oxidase are typically mitochondrial enzymes, their activity
decreases at the late blastula stage, synchronously with the rise in
activity of the mitochondrial enzymes. To explain this decrease of the
enzymatic activity, Deutsch and Gustafson (1952) have suggested the
formation of an inhibitor or the absorption of the enzyme at the intercellular surface. Alkaline phosphatase presents another problem. The
activity of this enzyme increases at the beginning of gastrulation like
the enzymes of the second group; nevertheless, in contrast to the
enzymes of the second group, the rise in activity of alkaline phosphatase
is not inhibited by lithium (Gustafson and Hasselberg, 1950).
Finally we must note that the mitochondrial distribution of enzymes
in the sea urchin egg is inferred from analogy with the observations
made on various tissues of vertebrates. As was pointed out by Brächet
(1960) the distribution of the enzymes in the sea urchin egg may differ
from that in other tissues. A direct study of the distribution of enzymes
in the sea urchin egg would remove this objection. We should also
remember that the ergastoplasm certainly plays an important role during
the differentiation of the egg. Ribosomal particles, a constituent of
ergastoplasm, are the sites of much if not all protein synthesis (Zamecnik,
1960). In the ultra-centrifugeable cytoplasmic particles of amphibian
eggs, the distribution of ribonucleic acid is altered by lithium ions
(Lallier, 1950,1954). Gustafson and Lenicque (1952,1955) have examined
the changes in the number and distribution of mitochondria in the
normal, vegetalized, and animalized sea urchin embryos. The counting
of the mitochondria is done in situ in whole embryos compressed under a
cover-slip. The mitochondria are counted in situ by the aid of a phasecontrast microscope or after vital staining with Nile blue sulphate.
During segmentation, the increase in the number of mitochondria
follows an S-shaped curve. This curve closely resembles the one observed
when measuring the increase of oxygen consumption during the same