MORPHOGENESIS IN STENTOR
15
simply that they have insufficient material to do so. Weisz (1948) produced still smaller stentors from tiny fragments and thought that there
was no lower limit to the size in which the form of Stentor can theoretically be manifested, the actual limit in practice being due merely to
physiological disturbances. Starting with dwarf stentors produced by
starvation, I have obtained tiny perfect stentors only γ ^ the volume
of the largest pre-starvation animals. The shape and form of these
miniature stentors, smaller than any found in nature, was altogether
regular, but I noted an unusual disproportion in the size of their parts.
The oral membranelles were in length and breadth about the same as
those of the largest animals and the pigmented stripes were also disproportionately wide (Tartar, 1960a). Therefore it appears that the
units of structure, such as membranelles and pigment bands are the
same in the smallest as in the largest animals. Failure of still smaller
fragments to regenerate the perfect form, though they survived well
and did produce a short row of membranelles, may therefore be simply
for the reason that mechanical difficulties are encountered when a very
tiny Stentor tries to produce a sharp coiling of relatively huge membranelles in stomatogenesis. The minimum size of regenerants then becomes
a sort of practical problem of constructional possibilities. Yet if it
should be confirmed that in ciliates and flagellates the units of ectoplasmic structure are of a fixed size, this would indeed constitute a
theoretically important feature of morphogenesis in Protozoa.
B. Upper Limits
Fusion masses of as many as 100 stentors have been grafted together
as a protoplasmic continuum (Tartar, 1954). These and smaller fusion
masses survive well and even live longer than starved normal cells,
apparently because they have much substance to draw upon. There
seems to be no upper physiological size limit since these masses do not
appear necrotic for a long time. Possibly this is because they became
pancake shaped and not much thicker than the normal Stentor so that
gaseous exchange to the interior was not a problem. Masses of fifteen
or more animals generally regenerated without producing mouthparts
and they were never able to organize the whole into any shape which
could be called a single giant Stentor.
It would appear that there is in Stentor a maximum organizational
mass, beyond which the normative morphogenetic capabilities of Stentor
are simply unable to cope. What the significance of this may be we
cannot yet say. It might be that in some way stentors 'pace off' certain
lengths of their striping or 'count' and control the number of stripes, and
that such integrative geometric processes can find no normal reference
from which to operate in masses of huge dimensions. For instance,
15
simply that they have insufficient material to do so. Weisz (1948) produced still smaller stentors from tiny fragments and thought that there
was no lower limit to the size in which the form of Stentor can theoretically be manifested, the actual limit in practice being due merely to
physiological disturbances. Starting with dwarf stentors produced by
starvation, I have obtained tiny perfect stentors only γ ^ the volume
of the largest pre-starvation animals. The shape and form of these
miniature stentors, smaller than any found in nature, was altogether
regular, but I noted an unusual disproportion in the size of their parts.
The oral membranelles were in length and breadth about the same as
those of the largest animals and the pigmented stripes were also disproportionately wide (Tartar, 1960a). Therefore it appears that the
units of structure, such as membranelles and pigment bands are the
same in the smallest as in the largest animals. Failure of still smaller
fragments to regenerate the perfect form, though they survived well
and did produce a short row of membranelles, may therefore be simply
for the reason that mechanical difficulties are encountered when a very
tiny Stentor tries to produce a sharp coiling of relatively huge membranelles in stomatogenesis. The minimum size of regenerants then becomes
a sort of practical problem of constructional possibilities. Yet if it
should be confirmed that in ciliates and flagellates the units of ectoplasmic structure are of a fixed size, this would indeed constitute a
theoretically important feature of morphogenesis in Protozoa.
B. Upper Limits
Fusion masses of as many as 100 stentors have been grafted together
as a protoplasmic continuum (Tartar, 1954). These and smaller fusion
masses survive well and even live longer than starved normal cells,
apparently because they have much substance to draw upon. There
seems to be no upper physiological size limit since these masses do not
appear necrotic for a long time. Possibly this is because they became
pancake shaped and not much thicker than the normal Stentor so that
gaseous exchange to the interior was not a problem. Masses of fifteen
or more animals generally regenerated without producing mouthparts
and they were never able to organize the whole into any shape which
could be called a single giant Stentor.
It would appear that there is in Stentor a maximum organizational
mass, beyond which the normative morphogenetic capabilities of Stentor
are simply unable to cope. What the significance of this may be we
cannot yet say. It might be that in some way stentors 'pace off' certain
lengths of their striping or 'count' and control the number of stripes, and
that such integrative geometric processes can find no normal reference
from which to operate in masses of huge dimensions. For instance,