56
H. W A R I S A N D P. K A L L I O
irradiation, in the doses applied, is negligible or very weak (Section IX),
while in the enucleate sections of Acetabularia it is strong (Haemmerling,
1956). In Micrasterias, the weak effect has only been observed in the
species thomasiana, the enucleate cells of which, when not irradiated,
may form new semicells with either five or three lobes, but after
irradiation only with three. Considering the fact that the development
of three lobes is not affected by irradiation and that the number three is
common to all the species experimented with, it seems to represent a
basic feature in the structure of the cytoplasm, while the number five
occurring in M. thomasiana seems to presuppose a residue of nuclear
substances in the cytoplasm.
Haemmerling (1963) has expressed the opinion that the inferiority of
the enucleate Micrasterias cells to those of Acetabularia might be due to
some injury to the cells, other than the removal of the nucleus, caused
by the procedure of enucleation. This opinion, however, is not consistent
with the results of nuclear splitting (Waris, 1958) or with the behaviour
of the enucleate cells derived from double cells (Section VII). To split
the nucleus, the same centrifugal force has been applied as will effect
enucleation. Nevertheless, one of the resulting daughter cells with a
deficient nucleus, though exhibiting symptoms of increasing morbidity,
remained alive for a month. On the other hand, the enucleate cells derived from double cells are similar, as regards shape and survival, to
those produced by the centrifuging of single cells, although the former
have not been subjected to the immediate effect of centrifuging. In fact,
centrifuging seems to be the gentlest procedure for achieving enucleation.
As to the longevity of the enucleate Spirogyra cells, those produced by
van Wisselingh (1909) by means of centrifugation remained alive for a
period ranging from about 2 weeks up to 2 months, and occasionally
even more, but they were included in threads also containing nucleate
cells, and a plasmatic connexion with these was not excluded, although
not noticed. I t may have been for this reason that van Wisselingh also
made attempts to isolate enucleate cells, but these experiments had to
be discontinued without any useful results. Thus new experiments with
Spirogyra would seem desirable.
V I I . Complex Cells
Complex cells result when cytokinesis is disturbed by different means.
The most effective methods are cold shock, heat, continuous illumination, treatment with dinitrophenol and centrifugation (Fig. 4). Other
less effective methods are exposure to a galvanic current or various
chemicals, and plasmolysis. Under adverse culture conditions complex
cells are often formed Spontaneously\
H. W A R I S A N D P. K A L L I O
irradiation, in the doses applied, is negligible or very weak (Section IX),
while in the enucleate sections of Acetabularia it is strong (Haemmerling,
1956). In Micrasterias, the weak effect has only been observed in the
species thomasiana, the enucleate cells of which, when not irradiated,
may form new semicells with either five or three lobes, but after
irradiation only with three. Considering the fact that the development
of three lobes is not affected by irradiation and that the number three is
common to all the species experimented with, it seems to represent a
basic feature in the structure of the cytoplasm, while the number five
occurring in M. thomasiana seems to presuppose a residue of nuclear
substances in the cytoplasm.
Haemmerling (1963) has expressed the opinion that the inferiority of
the enucleate Micrasterias cells to those of Acetabularia might be due to
some injury to the cells, other than the removal of the nucleus, caused
by the procedure of enucleation. This opinion, however, is not consistent
with the results of nuclear splitting (Waris, 1958) or with the behaviour
of the enucleate cells derived from double cells (Section VII). To split
the nucleus, the same centrifugal force has been applied as will effect
enucleation. Nevertheless, one of the resulting daughter cells with a
deficient nucleus, though exhibiting symptoms of increasing morbidity,
remained alive for a month. On the other hand, the enucleate cells derived from double cells are similar, as regards shape and survival, to
those produced by the centrifuging of single cells, although the former
have not been subjected to the immediate effect of centrifuging. In fact,
centrifuging seems to be the gentlest procedure for achieving enucleation.
As to the longevity of the enucleate Spirogyra cells, those produced by
van Wisselingh (1909) by means of centrifugation remained alive for a
period ranging from about 2 weeks up to 2 months, and occasionally
even more, but they were included in threads also containing nucleate
cells, and a plasmatic connexion with these was not excluded, although
not noticed. I t may have been for this reason that van Wisselingh also
made attempts to isolate enucleate cells, but these experiments had to
be discontinued without any useful results. Thus new experiments with
Spirogyra would seem desirable.
V I I . Complex Cells
Complex cells result when cytokinesis is disturbed by different means.
The most effective methods are cold shock, heat, continuous illumination, treatment with dinitrophenol and centrifugation (Fig. 4). Other
less effective methods are exposure to a galvanic current or various
chemicals, and plasmolysis. Under adverse culture conditions complex
cells are often formed Spontaneously\