DEVELOPMENT OF GASTROPODS
5
part of the egg. At the 4-cell stage they arrange themselves in each
quadrant into a narrow zone at the boundary between the clear animal
cytoplasm and the protein yolk. Very few droplets pass into the cells of
the first micromere quartet, somewhat more into the second, while the
cells of the third quartet get numerous fat droplets. In the D-quadrant,
nearly all the rest of the fatty yolk passes into 4d ; in the other quadrants
a more uniform distribution among the daughter cells takes place
(Clement and Lehmann, 1956).
The Golgi bodies ('Speichergranula') in Aplysia (Fig. 2) are at first
distributed rather evenly beneath the surface, but during maturation
they concentrate in a narrow ring at the boundary between the protein
yolk and fatty yolk zones. At cleavage they pass into particular cells :
the micromeres 2c and 2d and the macromeres A and B, but especially
(Fig. 2, I) the cells 3c, 3d, C and D (Ries and Gersch, 1936) (Fig. 2).
In Navanax a similar concentration of the Golgi bodies in a narrow
supra-equatorial ring takes place, but this occurs at the 4-cell stage;
both the first micromeres and macromeres get part of these corpuscles
(Worley and Worley, 1943).
In the pulmonates Limnaea
(Raven, 1945), Myxas,
Planorbis,
Succinea (Jura, 1960) and Arion (Lams, 1910) the mitochondria have a
strong tendency to concentrate around the maturation spindles; they
lie, often in rows, between the astral rays. This leads to their accumulation in the neighbourhood of the animal pole, where they come to lie in
the animal pole plasm and then become heaped up immediately beneath
the cortex. They are then distributed with the animal pole plasm.
In Aplysia
(Ries and Gersch, 1936; Attardo, 1957) and
Ilyanassa
(Clement and Lehmann, 1956) the mitochondria also accumulate around
the animal pole. In Aplysia they pass mainly into the first micromeres
la-Id and the cells 2a, 2b, 3a and 3b. At the 24-cell stage the trochoblasts lc
2 and Id
2 are very rich in mitochondria. In Ilyanassa the cells
of the first three quartets of micromeres all get a rich supply of mitochondria; the rest passes mainly into the fourth micromeres 4a-4d,
whereas the cells 4A-4D only get few mitochondria.
Particular granules of an unknown nature have been observed by
Blochmann (1882) in the uncleaved egg of Neritina. During cleavage
they become localized in two cells of the second quartet situated at left
and right, presumably the cells 2a
1 and 2c
1 .
In Physa (Wierzejski, 1905) and Limnaea (Raven, 1946; Minganti,
1950) dark granules become visible during early cleavage in the vegetal
asters of the cleavage spindles. They fuse to a number of dark bodies
very rich in RNA. At the 24-cell stage these bodies are shifted towards
the central ends of the macromeres 3A-3D ; at the next division they
pass into the cells of the fourth quartet.
5
part of the egg. At the 4-cell stage they arrange themselves in each
quadrant into a narrow zone at the boundary between the clear animal
cytoplasm and the protein yolk. Very few droplets pass into the cells of
the first micromere quartet, somewhat more into the second, while the
cells of the third quartet get numerous fat droplets. In the D-quadrant,
nearly all the rest of the fatty yolk passes into 4d ; in the other quadrants
a more uniform distribution among the daughter cells takes place
(Clement and Lehmann, 1956).
The Golgi bodies ('Speichergranula') in Aplysia (Fig. 2) are at first
distributed rather evenly beneath the surface, but during maturation
they concentrate in a narrow ring at the boundary between the protein
yolk and fatty yolk zones. At cleavage they pass into particular cells :
the micromeres 2c and 2d and the macromeres A and B, but especially
(Fig. 2, I) the cells 3c, 3d, C and D (Ries and Gersch, 1936) (Fig. 2).
In Navanax a similar concentration of the Golgi bodies in a narrow
supra-equatorial ring takes place, but this occurs at the 4-cell stage;
both the first micromeres and macromeres get part of these corpuscles
(Worley and Worley, 1943).
In the pulmonates Limnaea
(Raven, 1945), Myxas,
Planorbis,
Succinea (Jura, 1960) and Arion (Lams, 1910) the mitochondria have a
strong tendency to concentrate around the maturation spindles; they
lie, often in rows, between the astral rays. This leads to their accumulation in the neighbourhood of the animal pole, where they come to lie in
the animal pole plasm and then become heaped up immediately beneath
the cortex. They are then distributed with the animal pole plasm.
In Aplysia
(Ries and Gersch, 1936; Attardo, 1957) and
Ilyanassa
(Clement and Lehmann, 1956) the mitochondria also accumulate around
the animal pole. In Aplysia they pass mainly into the first micromeres
la-Id and the cells 2a, 2b, 3a and 3b. At the 24-cell stage the trochoblasts lc
2 and Id
2 are very rich in mitochondria. In Ilyanassa the cells
of the first three quartets of micromeres all get a rich supply of mitochondria; the rest passes mainly into the fourth micromeres 4a-4d,
whereas the cells 4A-4D only get few mitochondria.
Particular granules of an unknown nature have been observed by
Blochmann (1882) in the uncleaved egg of Neritina. During cleavage
they become localized in two cells of the second quartet situated at left
and right, presumably the cells 2a
1 and 2c
1 .
In Physa (Wierzejski, 1905) and Limnaea (Raven, 1946; Minganti,
1950) dark granules become visible during early cleavage in the vegetal
asters of the cleavage spindles. They fuse to a number of dark bodies
very rich in RNA. At the 24-cell stage these bodies are shifted towards
the central ends of the macromeres 3A-3D ; at the next division they
pass into the cells of the fourth quartet.