6
VANCE TARTAR
and increasing only by growth in length and by multiplicative replication of new stripes. Formation of new pigment bands by splitting of the
old ones indicates this and can be observed. Another indication is that
nucleated endoplasmic spheres, deprived of the entire cortex with its
lateral striping, persist for two or more days without disintegration but
never regenerate, being unable to produce striping (and kinetosomes?)
de novo (Tartar, 1956c). Other parts are derived from the lateral striping.
The holdfast is clearly such an elaboration of posterior stripe-ends.
Feeding organelles are the most conspicuous elaboration, arising from a
primordium appearing within the lateral striping and intimately correlated with its pattern, as we shall see. In the related Fabrea (VilleneuveBrachon, 1940) silver staining indicates that the ciliary basal bodies of
the anlagen originate from multiplication of these kinetosomes in the
adjacent lateral ciliary rows. Hence there is genuine epigenesis of the
derived structures, while the fundamental organization grows only from
its like.
The macronucleus is also a derived structure, originating from products
of the micronuclear syncaryon after conjugation. The micronucleus is
basic, new ones arising only by replication of the old. (Chromosomes as a
set are basic parts of a nucleus, for if one type of chromosome is lost it
cannot be regenerated from the remainder.) Yet in the vegetative life of
Stentor the macronucleus behaves as a basic part. Theoretically it should
be replaceable from the scattered micronuclei; but surprisingly enough
emacronucleated stentors never do this, remaining functionally enucleate (because the micronuclei are ineffective in vegetative life) and die
in a week. After partial enucleation, the macronuclear chain is regenerated only if at least one node is left. Regeneration is by growth from the
remainder, for if the node is pre-labelled with radioactive phosphorus,
activity is uniformly distributed throughout the regenerated chain (de
Terra, 1958). This compensatory nuclear increase occurs only after
primordium formation in regeneration or reorganization.
Even tiny nucleated fragments only j j ^ the size of the largest specimens can regenerate feeding organelles and tail poles in proportion to
their size. Here we may speak of a complete individualization in which a
small part becomes a whole, for the accomplishment is even greater than
in cell reproduction. The fragment heals and thus survives because it
maintains the cell type of organization. It retains that portion of the
original striping which it bears and which undoubtedly determines the
polarity of the regenerant as well as producing the derived organelles.
A normal Stentor therefore potentially can form about 125 individuals,
presuming each cut fragment can be supplied with a nuclear node. And
in some ciliates like Ichthyoptherius (Mugard, 1948) multiple division
occurs in which the lateral striping is autonomously broken into tiny
VANCE TARTAR
and increasing only by growth in length and by multiplicative replication of new stripes. Formation of new pigment bands by splitting of the
old ones indicates this and can be observed. Another indication is that
nucleated endoplasmic spheres, deprived of the entire cortex with its
lateral striping, persist for two or more days without disintegration but
never regenerate, being unable to produce striping (and kinetosomes?)
de novo (Tartar, 1956c). Other parts are derived from the lateral striping.
The holdfast is clearly such an elaboration of posterior stripe-ends.
Feeding organelles are the most conspicuous elaboration, arising from a
primordium appearing within the lateral striping and intimately correlated with its pattern, as we shall see. In the related Fabrea (VilleneuveBrachon, 1940) silver staining indicates that the ciliary basal bodies of
the anlagen originate from multiplication of these kinetosomes in the
adjacent lateral ciliary rows. Hence there is genuine epigenesis of the
derived structures, while the fundamental organization grows only from
its like.
The macronucleus is also a derived structure, originating from products
of the micronuclear syncaryon after conjugation. The micronucleus is
basic, new ones arising only by replication of the old. (Chromosomes as a
set are basic parts of a nucleus, for if one type of chromosome is lost it
cannot be regenerated from the remainder.) Yet in the vegetative life of
Stentor the macronucleus behaves as a basic part. Theoretically it should
be replaceable from the scattered micronuclei; but surprisingly enough
emacronucleated stentors never do this, remaining functionally enucleate (because the micronuclei are ineffective in vegetative life) and die
in a week. After partial enucleation, the macronuclear chain is regenerated only if at least one node is left. Regeneration is by growth from the
remainder, for if the node is pre-labelled with radioactive phosphorus,
activity is uniformly distributed throughout the regenerated chain (de
Terra, 1958). This compensatory nuclear increase occurs only after
primordium formation in regeneration or reorganization.
Even tiny nucleated fragments only j j ^ the size of the largest specimens can regenerate feeding organelles and tail poles in proportion to
their size. Here we may speak of a complete individualization in which a
small part becomes a whole, for the accomplishment is even greater than
in cell reproduction. The fragment heals and thus survives because it
maintains the cell type of organization. It retains that portion of the
original striping which it bears and which undoubtedly determines the
polarity of the regenerant as well as producing the derived organelles.
A normal Stentor therefore potentially can form about 125 individuals,
presuming each cut fragment can be supplied with a nuclear node. And
in some ciliates like Ichthyoptherius (Mugard, 1948) multiple division
occurs in which the lateral striping is autonomously broken into tiny