64
H. WARIS AND P. KALLIO
cedure (centrifugation) leading to these forms; (2) the many possibilities of combining different numbers of nuclei with different numbers of
cytoplasmic units; (3) the possibility of controlling the nuclear effect at
the point of action, which is partly based on the independence of the
spatial location of the nucleus in relation to the point of action (e.g.
septum formation) ; (4) the large sizes of the cells and the long distances
between two nuclei make it possible to treat (e.g. irradiate) different
parts of the cell separately (see Section IX).
In complex cells the nuclear effect is quantitatively reflected in three
events.
(a) The formation of the septum is dependent on some 'stimulus'
released by the nucleus after the disappearance of the nuclear membrane
(Kallio, 1951). The formation of the septum always begins late in the
enucleate isthmus and its later development and the end result (septum
formation or its retraction) are dependent on the magnitude of this
stimulus.
(b) Because the form of the semicell is closely correlated with the
nuclear effect present when it develops, different types of semicells are
formed simultaneously. Thus differences are seen in the size and form of
the semicells at each end of a heterocaryotic cell, but owing to the
equalizing effect of diffusion the differences are smaller than those between typical haploid and diploid cells. In a type II cell a larger and
more differentiated semicell develops at the nucleate than at the other
end, but often it resembles a haploid semicell whereas that formed at
the enucleate end is hypohaploid in shape. Many different forms intermediate between enucleate and haploid forms are met in complex cells.
The only new semicell formed in M. thomasiana type II cells is diploid
or sometimes hyperdiploid in form.
(c) The nuclear quantity has also some effect on the radiation, i.e. the
number of wings, as is seen in the polyploids (see Section VIII). Because
many different relationships in these quantitative characteristics are
present in the complex cells, the problem may be studied on different
scales. Particularly the effect of an abnormally weak nuclear influence
on radiation may be studied. These cells make possible also a study of a
hypohaploid nuclear effect during the intermitotic stage. Whereas an
increased nuclear effect has a tendency to increase the number of wings,
the opposite may be expected to happen when the nuclear effect is decreased (cf. Kallio, 1959). The diminished nuclear effect in the enucleate
isthmus of M. torreyi type II complex cells is often seen as defects in one
or sometimes both wings. Hence uniradiate enucleate cells are produced
from these cells. Owing to the large size of the complex cell the nuclear
effect may be less than in the haploid in the nucleate isthmus also, and
hence nucleate uniradiate cells may be produced.
H. WARIS AND P. KALLIO
cedure (centrifugation) leading to these forms; (2) the many possibilities of combining different numbers of nuclei with different numbers of
cytoplasmic units; (3) the possibility of controlling the nuclear effect at
the point of action, which is partly based on the independence of the
spatial location of the nucleus in relation to the point of action (e.g.
septum formation) ; (4) the large sizes of the cells and the long distances
between two nuclei make it possible to treat (e.g. irradiate) different
parts of the cell separately (see Section IX).
In complex cells the nuclear effect is quantitatively reflected in three
events.
(a) The formation of the septum is dependent on some 'stimulus'
released by the nucleus after the disappearance of the nuclear membrane
(Kallio, 1951). The formation of the septum always begins late in the
enucleate isthmus and its later development and the end result (septum
formation or its retraction) are dependent on the magnitude of this
stimulus.
(b) Because the form of the semicell is closely correlated with the
nuclear effect present when it develops, different types of semicells are
formed simultaneously. Thus differences are seen in the size and form of
the semicells at each end of a heterocaryotic cell, but owing to the
equalizing effect of diffusion the differences are smaller than those between typical haploid and diploid cells. In a type II cell a larger and
more differentiated semicell develops at the nucleate than at the other
end, but often it resembles a haploid semicell whereas that formed at
the enucleate end is hypohaploid in shape. Many different forms intermediate between enucleate and haploid forms are met in complex cells.
The only new semicell formed in M. thomasiana type II cells is diploid
or sometimes hyperdiploid in form.
(c) The nuclear quantity has also some effect on the radiation, i.e. the
number of wings, as is seen in the polyploids (see Section VIII). Because
many different relationships in these quantitative characteristics are
present in the complex cells, the problem may be studied on different
scales. Particularly the effect of an abnormally weak nuclear influence
on radiation may be studied. These cells make possible also a study of a
hypohaploid nuclear effect during the intermitotic stage. Whereas an
increased nuclear effect has a tendency to increase the number of wings,
the opposite may be expected to happen when the nuclear effect is decreased (cf. Kallio, 1959). The diminished nuclear effect in the enucleate
isthmus of M. torreyi type II complex cells is often seen as defects in one
or sometimes both wings. Hence uniradiate enucleate cells are produced
from these cells. Owing to the large size of the complex cell the nuclear
effect may be less than in the haploid in the nucleate isthmus also, and
hence nucleate uniradiate cells may be produced.