MORPHOGENESIS IN STENTOR
7
patches which become separate cells and individualities. In either case,
the part becomes a whole when it is no longer in intimate structural
relation with other parts.
III. Adjustment of Proportionality and Arrangement of Parts
Lateral striping is prevented from becoming abnormally long by the
onset of fission in which the stripes are cut in two, and if there are too
few stripes new ones are added by rapid stripe multiplication. A small
fragment begins with short stripes far less in number than the normal
complement of about 200 but the stripes then multiply at the line of
healing and increase in length as the tiny Stentor grows until a fully
normal complement is restored. Similarly, longitudinal halves of stentors, with half the normal number of stripes do not remain permanently
narrow, for compensatory stripe multiplication occurs; but this increase
stops when the normal number is achieved. Evidently there is some
means for controlling the upper limit, and such a control is inferred
from the finding that of several salts tested lithium chloride alone produces an increase in the number of stripes above normal, the treated
cell becoming extraordinarily broad and even transforming into a doublet
stentor (Tartar, 1957a). It is of course most interesting that the lithium
ion has enduring morphogenetic effects on stentors as well as on embryos.
Stentors are capable of many other minor adjustments, always tending toward the normal form. Morgan (1901) found that when stentors
are cut in two transversely, the too-large feeding organelles of the anterior fragment somehow decrease in size, as does the disproportionate
tail of the posterior piece. Much more striking is the behaviour of excised,
nucleated heads (Fig. 3). These discs fold to cover the exposed endoFIG. 3. Reconstruction in an excised, nucleated head. Feeding organelles and frontal
field excised as indicated. Head folds on itself to heal. Membranellar band gradually
reduces in length and mouthparts in size as lateral striping grows out, producing a perfect
tiny stentor of normally proportionate parts.
plasm and in the course of several days the enormously disproportionate
feeding organelles are gradually reduced to proper size, resorbed parts
apparently furnishing the material for outgrowth of lateral striping to
produce the normal tail and cell shape (Tartar, 1960a). By a remarkable
morphollaxis the bizarre fragment is thus remodelled as a tiny normal
Stentor.
7
patches which become separate cells and individualities. In either case,
the part becomes a whole when it is no longer in intimate structural
relation with other parts.
III. Adjustment of Proportionality and Arrangement of Parts
Lateral striping is prevented from becoming abnormally long by the
onset of fission in which the stripes are cut in two, and if there are too
few stripes new ones are added by rapid stripe multiplication. A small
fragment begins with short stripes far less in number than the normal
complement of about 200 but the stripes then multiply at the line of
healing and increase in length as the tiny Stentor grows until a fully
normal complement is restored. Similarly, longitudinal halves of stentors, with half the normal number of stripes do not remain permanently
narrow, for compensatory stripe multiplication occurs; but this increase
stops when the normal number is achieved. Evidently there is some
means for controlling the upper limit, and such a control is inferred
from the finding that of several salts tested lithium chloride alone produces an increase in the number of stripes above normal, the treated
cell becoming extraordinarily broad and even transforming into a doublet
stentor (Tartar, 1957a). It is of course most interesting that the lithium
ion has enduring morphogenetic effects on stentors as well as on embryos.
Stentors are capable of many other minor adjustments, always tending toward the normal form. Morgan (1901) found that when stentors
are cut in two transversely, the too-large feeding organelles of the anterior fragment somehow decrease in size, as does the disproportionate
tail of the posterior piece. Much more striking is the behaviour of excised,
nucleated heads (Fig. 3). These discs fold to cover the exposed endoFIG. 3. Reconstruction in an excised, nucleated head. Feeding organelles and frontal
field excised as indicated. Head folds on itself to heal. Membranellar band gradually
reduces in length and mouthparts in size as lateral striping grows out, producing a perfect
tiny stentor of normally proportionate parts.
plasm and in the course of several days the enormously disproportionate
feeding organelles are gradually reduced to proper size, resorbed parts
apparently furnishing the material for outgrowth of lateral striping to
produce the normal tail and cell shape (Tartar, 1960a). By a remarkable
morphollaxis the bizarre fragment is thus remodelled as a tiny normal
Stentor.