312
ELVEZIO GHIRARDELLI
reached their maximum growth, they flatten t o form small plaques
which can be clearly seen in tangential sections of the nucleus; their
number increases remarkably during the second period of growth, when
the synthesis of the specific ovular proteins is most active and the oocytes
have exceeded 30 p in diameter and after the chromosomes at diplotene
have taken on their characteristic lampbrush appearance. (Fig. 17) ;
According to BordAs the grains are on the outside of the nuclear
membrane in the knots of a net-like formation and are equivalent to
irregularly shaped kariosomes ; this is, however, contradicted by their
negative Feulgen reaction.
A relationship has been observed between the quantity of ribonucleic acid (RNA) present in the plaques of the nuclear net and the
FIG. 17. Oocyte of Spadella in the 2nd period of growth. Around the nucleus, the small
plaques of RNA positive substance. I n the cytoplasm the RNA positive substance
i s placed in concentric zones. I n the nucleus the lamp-brush chromosorncs can be
seen.
RNA in the cytoplasm. In the first and second periods of growth, i.e.
when the nuclei are in synaptic stages, in the cytoplasm there is an
increase of the materials containing RNA. This material in some cases
is distributed in concentric rings around the nucleus. In the third
period, i.e. at vitellogenesis, both the cytoplasm and the small plaques
show a lesser quantity of RNA. There is, therefore, a course of events
in the distribution of the RNA-positive materials in every way similar
to that observed in the oocytes of other animals. I n the nuclear net
the same process can be observed, as far as RNA-positive material is
concerned, as in the nucleoli of other eggs.
The greatest concentration of ribonucleoproteins occurs gcnerally in
the smaller oocytes placed near the seminal pouch ; this may support
the idea of BordAs (1920) that the seminal pouch may have trophic
functions, producing substances which may be used by the oocytes.
It does not seem, however, that this hypothesis can be extended, as
ELVEZIO GHIRARDELLI
reached their maximum growth, they flatten t o form small plaques
which can be clearly seen in tangential sections of the nucleus; their
number increases remarkably during the second period of growth, when
the synthesis of the specific ovular proteins is most active and the oocytes
have exceeded 30 p in diameter and after the chromosomes at diplotene
have taken on their characteristic lampbrush appearance. (Fig. 17) ;
According to BordAs the grains are on the outside of the nuclear
membrane in the knots of a net-like formation and are equivalent to
irregularly shaped kariosomes ; this is, however, contradicted by their
negative Feulgen reaction.
A relationship has been observed between the quantity of ribonucleic acid (RNA) present in the plaques of the nuclear net and the
FIG. 17. Oocyte of Spadella in the 2nd period of growth. Around the nucleus, the small
plaques of RNA positive substance. I n the cytoplasm the RNA positive substance
i s placed in concentric zones. I n the nucleus the lamp-brush chromosorncs can be
seen.
RNA in the cytoplasm. In the first and second periods of growth, i.e.
when the nuclei are in synaptic stages, in the cytoplasm there is an
increase of the materials containing RNA. This material in some cases
is distributed in concentric rings around the nucleus. In the third
period, i.e. at vitellogenesis, both the cytoplasm and the small plaques
show a lesser quantity of RNA. There is, therefore, a course of events
in the distribution of the RNA-positive materials in every way similar
to that observed in the oocytes of other animals. I n the nuclear net
the same process can be observed, as far as RNA-positive material is
concerned, as in the nucleoli of other eggs.
The greatest concentration of ribonucleoproteins occurs gcnerally in
the smaller oocytes placed near the seminal pouch ; this may support
the idea of BordAs (1920) that the seminal pouch may have trophic
functions, producing substances which may be used by the oocytes.
It does not seem, however, that this hypothesis can be extended, as