ULTRASTRUCTURE OF DEVELOPING AMPHIBIAN EGG 163
The method of formation of the cortical granules, as described by Balinsky and Devis, involves the enlargement of one of the vesicles inside a
cluster of Golgi elements (Fig. 22). As this vesicle enlarges, its previously
optically empty cavity becomes filled with the homogeneous material that
characterizes such bodies. This body, which has enlarged to form a cortical
granule, separates from the enveloping Golgi elements. The process is then,
presumably, repeated many times within this same organelle.
Jj.. Pigment Granules
After yolk formation has been initiated, pigment granules appear in the
peripheral cytoplasm of oocytes. They can be recognized as definitive
structures by the time a very substantial amount of yolk fills the cytoplasm
(Kemp, 1956). Pigment granules were first studied with the electron microscope by Dollander (1954, 1956). He found these granules to be about
0.3 μ in diameter, in eggs from Triton (= Triturus alpestris). Each granule
consisted of a mass of about twenty microgranules that was enveloped by
a barely evident membrane. Similar observations were made by Wischnitzer
(1957), who examined oocytes from Triturus viridescens. Subsequently,
Wartenberg and Schmidt (1961), working with Rana temporaria, observed
that the pigment granules, located at the animal pole, were about twice as
large as those elsewhere. In this species they also noted that each granule
consists essentially of a homogeneous dense matrix, containing coarse
internal structures surrounded by a delicate membrane. In a comparative
study on amphibians later that year, Wartenberg (1962) clearly showed
that the pigment granules belong to two types. In urodeles (see Fig. 19)
these bodies consist of numerous microgranules (0.05-0.10 μ in diameter),
whereas in anurans the granules are more complex. In the later form, each
body contains a peripheral layer of coarse granules, inside of which is a
dense matrix that surrounds a cluster of structures that have a "negative"
appearance. The cluster consists of elements having the appearance of
concentric rings, parallel lines, fine vesicles, granules, and crystalloid lattice
structures.
5. Glycogen
The presence of glycogen in the cytoplasm of amphibian oocytes has been
reported by Brächet and Needham (1935). Brächet (1960) claims that this
material exists in the form of small granules or macromolecules. Electronmicroscope identification of glycogen in tissues has been indirect. Baker
(1963) feels that positive localization and identification can be made by
means of a freeze-thawing technique. He identified glycogen as aggregates
of densely stained particles arranged in rosette fashion in the ground substance. The rosettes are readily distinguishable from smaller, less dense,
The method of formation of the cortical granules, as described by Balinsky and Devis, involves the enlargement of one of the vesicles inside a
cluster of Golgi elements (Fig. 22). As this vesicle enlarges, its previously
optically empty cavity becomes filled with the homogeneous material that
characterizes such bodies. This body, which has enlarged to form a cortical
granule, separates from the enveloping Golgi elements. The process is then,
presumably, repeated many times within this same organelle.
Jj.. Pigment Granules
After yolk formation has been initiated, pigment granules appear in the
peripheral cytoplasm of oocytes. They can be recognized as definitive
structures by the time a very substantial amount of yolk fills the cytoplasm
(Kemp, 1956). Pigment granules were first studied with the electron microscope by Dollander (1954, 1956). He found these granules to be about
0.3 μ in diameter, in eggs from Triton (= Triturus alpestris). Each granule
consisted of a mass of about twenty microgranules that was enveloped by
a barely evident membrane. Similar observations were made by Wischnitzer
(1957), who examined oocytes from Triturus viridescens. Subsequently,
Wartenberg and Schmidt (1961), working with Rana temporaria, observed
that the pigment granules, located at the animal pole, were about twice as
large as those elsewhere. In this species they also noted that each granule
consists essentially of a homogeneous dense matrix, containing coarse
internal structures surrounded by a delicate membrane. In a comparative
study on amphibians later that year, Wartenberg (1962) clearly showed
that the pigment granules belong to two types. In urodeles (see Fig. 19)
these bodies consist of numerous microgranules (0.05-0.10 μ in diameter),
whereas in anurans the granules are more complex. In the later form, each
body contains a peripheral layer of coarse granules, inside of which is a
dense matrix that surrounds a cluster of structures that have a "negative"
appearance. The cluster consists of elements having the appearance of
concentric rings, parallel lines, fine vesicles, granules, and crystalloid lattice
structures.
5. Glycogen
The presence of glycogen in the cytoplasm of amphibian oocytes has been
reported by Brächet and Needham (1935). Brächet (1960) claims that this
material exists in the form of small granules or macromolecules. Electronmicroscope identification of glycogen in tissues has been indirect. Baker
(1963) feels that positive localization and identification can be made by
means of a freeze-thawing technique. He identified glycogen as aggregates
of densely stained particles arranged in rosette fashion in the ground substance. The rosettes are readily distinguishable from smaller, less dense,