4
VANCE TARTAR
posterior boundary of this anterior mass defines precisely the future
division furrow which thus separates this mass into the anterior cell
(Tartar, 1959a). The precise translocation of this material reminds one of
the migration of granules and polar plasm in early development of certain eggs.
In the production of new individuals, therefore, as much as possible
of the old is passed on directly, with new parts formed only when unavoidable, and this is generally true for ciliates and flagellates. There is a
direct inheritance of parts which go to make up the form, different for
each of the two daughter cells, together with a true epigenesis or elaboration of new parts, notably in the development of the oral primordium
for the posterior cell.
C. Reorganization of an Individual
Occasionally stentors produce a new set of feeding organelles replacing the mouthparts and adjacent membranelies of the original set which
are then resorbed. Although there may be other causes, this replacement occurs if for any reason the original feeding organelles are too
small in proportion to the cell though perfect in their construction, for
these organelles apparently never increase in situ but only through
primordium formation and development. Alternatively, reorganization
may occur if the nucleus is too small, as when all but one or two of the
nodes are excised; for oddly enough the nucleus is unable to undergo
compensatory hypertrophy except as an accompaniment of primordium
formation (Schwartz, 1935). 'Reorganization' is therefore something of a
misnomer because there is no widespread re-organization; nor is there
good evidence that this process is to replace worn-out ingestive structures, as was once thought. Rather should we note that it quickly
registers whether any of the parts which make up the total form are
disproportionate; reorganization is one of the means for correcting disproportionality, of which others will be discussed later.
D. Regeneration
Regeneration in Stentor is of wide range. Excised holdfasts are replaced in about one hour, even without benefit of the nucleus. This is
understandable because according to Andrews (1945) the holdfast is
merely a modification of the posterior ends of the lateral stripes and
therefore should not demand synthesis of new parts, which apparently
requires the presence of the nucleus. It has also been found that new
posterior poles and holdfasts can arise in a novel way, seldom if ever
occurring in nature (Tartar, 1956b). Aboral halves, produced by cutting
the cell in two longitudinally, fold upon themselves to heal. The striping
is rather sharply bent at the fold (Fig. 2). If this configuration is main-
VANCE TARTAR
posterior boundary of this anterior mass defines precisely the future
division furrow which thus separates this mass into the anterior cell
(Tartar, 1959a). The precise translocation of this material reminds one of
the migration of granules and polar plasm in early development of certain eggs.
In the production of new individuals, therefore, as much as possible
of the old is passed on directly, with new parts formed only when unavoidable, and this is generally true for ciliates and flagellates. There is a
direct inheritance of parts which go to make up the form, different for
each of the two daughter cells, together with a true epigenesis or elaboration of new parts, notably in the development of the oral primordium
for the posterior cell.
C. Reorganization of an Individual
Occasionally stentors produce a new set of feeding organelles replacing the mouthparts and adjacent membranelies of the original set which
are then resorbed. Although there may be other causes, this replacement occurs if for any reason the original feeding organelles are too
small in proportion to the cell though perfect in their construction, for
these organelles apparently never increase in situ but only through
primordium formation and development. Alternatively, reorganization
may occur if the nucleus is too small, as when all but one or two of the
nodes are excised; for oddly enough the nucleus is unable to undergo
compensatory hypertrophy except as an accompaniment of primordium
formation (Schwartz, 1935). 'Reorganization' is therefore something of a
misnomer because there is no widespread re-organization; nor is there
good evidence that this process is to replace worn-out ingestive structures, as was once thought. Rather should we note that it quickly
registers whether any of the parts which make up the total form are
disproportionate; reorganization is one of the means for correcting disproportionality, of which others will be discussed later.
D. Regeneration
Regeneration in Stentor is of wide range. Excised holdfasts are replaced in about one hour, even without benefit of the nucleus. This is
understandable because according to Andrews (1945) the holdfast is
merely a modification of the posterior ends of the lateral stripes and
therefore should not demand synthesis of new parts, which apparently
requires the presence of the nucleus. It has also been found that new
posterior poles and holdfasts can arise in a novel way, seldom if ever
occurring in nature (Tartar, 1956b). Aboral halves, produced by cutting
the cell in two longitudinally, fold upon themselves to heal. The striping
is rather sharply bent at the fold (Fig. 2). If this configuration is main-