8
VANCE TARTAR
In grafts of two animals, or when extra heads or tails are transplanted
on to a single individual, the duplicate parts usually fuse together; and
just those portions of the membranellar band or of the cortical striping
between the duplicated tails are resorbed as is required for unification.
In doublet stentors the normal form is often begun by resorption of one set
of mouthparts. If the head is circumscribed and merely rotated through
180°, healing is very neat and feeding continues. Only the pattern of the
cell is changed in a subtle way, yet the mistake is eventually corrected
(Fig. 4). Mouthparts become detached from the membranellar band,
Fi«. 4. Response to minor alteration of the cell pattern. Head is circumscribed and
rotated through 180°. Ends of the membranellar band meet and fuse, with mouthparts
separating into the frontal field. Old mouthparts resorbed as primordium forms in proper
location and part of peristome is resorbed to permit new parts to enter the frontal field,
restoring the normal pattern and relation of parts.
move into the frontal field and are resorbed, whereupon an oral primordium appears on the opposite side in the normal primordium site and a
section of the old band is dissolved to permit entrance of a new set of
mouthparts, now in the proper location (Tartar, 1960a). Departures
from the normal form and pattern generally elicit appropriate means for
their correction.
Cell pattern can also be disarranged by circumscribing a Stentor and
rotating the anterior half through 180° on the posterior portion. Again
we have a subtle alteration which does not appear to interfere with
normal functions yet is never tolerated. When the incision is at the midlevel of the axis or somewhat forward and regeneration is induced, the
cortical structures of the anterior part are resorbed as those of the posterior part extend and take over (Tartar, 1956a). When the cut is made
posterior to the mid-line, it is the posterior stripes which disappear
(Uhlig, 1959). When the cut is made in the middle and regeneration is
not induced, certain stripes in each half penetrate through those of the
other and a doublet stentor is produced, jet this doublet will eventually
revert to the single form (Tartar, 1959b). Whether directly by resorption or by the circuitous route of doublet formation, these specimens
eventually return to the normal pattern.
In spite of these remarkable tendencies to revert to normal, extreme
abnormalities of form develop in some strains of S. coeruleus without
VANCE TARTAR
In grafts of two animals, or when extra heads or tails are transplanted
on to a single individual, the duplicate parts usually fuse together; and
just those portions of the membranellar band or of the cortical striping
between the duplicated tails are resorbed as is required for unification.
In doublet stentors the normal form is often begun by resorption of one set
of mouthparts. If the head is circumscribed and merely rotated through
180°, healing is very neat and feeding continues. Only the pattern of the
cell is changed in a subtle way, yet the mistake is eventually corrected
(Fig. 4). Mouthparts become detached from the membranellar band,
Fi«. 4. Response to minor alteration of the cell pattern. Head is circumscribed and
rotated through 180°. Ends of the membranellar band meet and fuse, with mouthparts
separating into the frontal field. Old mouthparts resorbed as primordium forms in proper
location and part of peristome is resorbed to permit new parts to enter the frontal field,
restoring the normal pattern and relation of parts.
move into the frontal field and are resorbed, whereupon an oral primordium appears on the opposite side in the normal primordium site and a
section of the old band is dissolved to permit entrance of a new set of
mouthparts, now in the proper location (Tartar, 1960a). Departures
from the normal form and pattern generally elicit appropriate means for
their correction.
Cell pattern can also be disarranged by circumscribing a Stentor and
rotating the anterior half through 180° on the posterior portion. Again
we have a subtle alteration which does not appear to interfere with
normal functions yet is never tolerated. When the incision is at the midlevel of the axis or somewhat forward and regeneration is induced, the
cortical structures of the anterior part are resorbed as those of the posterior part extend and take over (Tartar, 1956a). When the cut is made
posterior to the mid-line, it is the posterior stripes which disappear
(Uhlig, 1959). When the cut is made in the middle and regeneration is
not induced, certain stripes in each half penetrate through those of the
other and a doublet stentor is produced, jet this doublet will eventually
revert to the single form (Tartar, 1959b). Whether directly by resorption or by the circuitous route of doublet formation, these specimens
eventually return to the normal pattern.
In spite of these remarkable tendencies to revert to normal, extreme
abnormalities of form develop in some strains of S. coeruleus without