ULTRASTRUCTURE OF DEVELOPING AMPHIBIAN EGG 155
peripherally, clusters of mitochondria separate from the yolk nucleus. Some
of them continue their peripheral migration and pass without colliding
with the yolk platelets that are moving in the opposite direction. The other
clusters of mitochondria move laterally and are distributed throughout the
cytoplasm. Finally, when the oocyte is ^1000 μ in diameter, the forwardmoving mitochondria reach the surface where they spread out between the
layer of cortical granules and the outer margin of the yolk mass. At no time
have Balinsky and Devis found yolk platelets associated with the yolk
nucleus.
2. Golgi Complex
It has now been established that the most reliable means of identifying
the Golgi complex is on the basis of its ultrastructure (Palay, 1958). This
organelle has been studied in oocytes from Triturus viridescens both before
and after the initiation of vitellogenesis (Wischnitzer, 1962b). In the former
case, the elements making up each complex were found to assume linear,
arc, or C-shaped arrangements. Such organelle complexes consist primarily
of small (150-600 A) vesicles as well as a few flattened cisternae (Fig. 16).
After vitellogenesis has been initiated, the elements of the complex exhibit
the same arrangements as before. A very marked reduction in the number of
small vesicles associated with individual complexes, is, however, apparent.
At this time, cisternae, usually four in number, are the predominant elements (Fig. 17).
The distribution of the Golgi complex, as seen by electron microscopy,
also appears to vary with age. These are usually located, in very young
oocytes, in the peripheral cytoplasm adjacent to the surface of the egg
(Wischnitzer, 1962b; Wartenberg, 1962; Balinsky and Devis, 1963). Subsequently, they are found in the yolk-forming zone, and later they are
distributed throughout the yolky cytoplasm.
3. Annulate
Lamellae
Cytoplasmic membranes having an ultrastructure similar to that of the
nuclear envelope have been observed in a variety of somatic and germinal
cells, as well as in normal and malignant cells. Such membranes have been
observed most commonly in the developing egg. In amphibians, the annulate lamellae can appear both as individual sheets (Wischnitzer, 1960)
and as complex membranous systems (Kessel, 1963; Balinsky and Devis,
1963).
apparently by coalescence, have become very short cisternae. Mitochondria (m) and
vesicles (v) are also evident. X 45,000.
FIG. 17. An electron micrograph of a region in the cytoplasm of an older, yolkcontaining oocyte. The Golgi complex (gc) consists of several long, parallel cisternae. Mitochondria (m) and vesicles (v) are also present. X 32,000.
peripherally, clusters of mitochondria separate from the yolk nucleus. Some
of them continue their peripheral migration and pass without colliding
with the yolk platelets that are moving in the opposite direction. The other
clusters of mitochondria move laterally and are distributed throughout the
cytoplasm. Finally, when the oocyte is ^1000 μ in diameter, the forwardmoving mitochondria reach the surface where they spread out between the
layer of cortical granules and the outer margin of the yolk mass. At no time
have Balinsky and Devis found yolk platelets associated with the yolk
nucleus.
2. Golgi Complex
It has now been established that the most reliable means of identifying
the Golgi complex is on the basis of its ultrastructure (Palay, 1958). This
organelle has been studied in oocytes from Triturus viridescens both before
and after the initiation of vitellogenesis (Wischnitzer, 1962b). In the former
case, the elements making up each complex were found to assume linear,
arc, or C-shaped arrangements. Such organelle complexes consist primarily
of small (150-600 A) vesicles as well as a few flattened cisternae (Fig. 16).
After vitellogenesis has been initiated, the elements of the complex exhibit
the same arrangements as before. A very marked reduction in the number of
small vesicles associated with individual complexes, is, however, apparent.
At this time, cisternae, usually four in number, are the predominant elements (Fig. 17).
The distribution of the Golgi complex, as seen by electron microscopy,
also appears to vary with age. These are usually located, in very young
oocytes, in the peripheral cytoplasm adjacent to the surface of the egg
(Wischnitzer, 1962b; Wartenberg, 1962; Balinsky and Devis, 1963). Subsequently, they are found in the yolk-forming zone, and later they are
distributed throughout the yolky cytoplasm.
3. Annulate
Lamellae
Cytoplasmic membranes having an ultrastructure similar to that of the
nuclear envelope have been observed in a variety of somatic and germinal
cells, as well as in normal and malignant cells. Such membranes have been
observed most commonly in the developing egg. In amphibians, the annulate lamellae can appear both as individual sheets (Wischnitzer, 1960)
and as complex membranous systems (Kessel, 1963; Balinsky and Devis,
1963).
apparently by coalescence, have become very short cisternae. Mitochondria (m) and
vesicles (v) are also evident. X 45,000.
FIG. 17. An electron micrograph of a region in the cytoplasm of an older, yolkcontaining oocyte. The Golgi complex (gc) consists of several long, parallel cisternae. Mitochondria (m) and vesicles (v) are also present. X 32,000.