. The biology of Stentor. Stentor. POLARITY 203 supplied sketches from my own experiments (including Fig. 44), which may therefore be regarded as generally Fig. 56. Observations regarding induction of stomatogenesis by the posterior end. A. In an oral half of a stage-3 divider the anlage was not resorbed but extended all the way to the posterior pole and produced no mouthparts, presumably because inducing region is anterior to the pole itself. B. Two extra tail poles engrafted led to multiple stomato- genesis, with complete but ectopic gullet (x). C. Specimen with two tail poles
. The biology of Stentor. Stentor. POLARITY 203 supplied sketches from my own experiments (including Fig. 44), which may therefore be regarded as generally Fig. 56. Observations regarding induction of stomatogenesis by the posterior end. A. In an oral half of a stage-3 divider the anlage was not resorbed but extended all the way to the posterior pole and produced no mouthparts, presumably because inducing region is anterior to the pole itself. B. Two extra tail poles engrafted led to multiple stomato- genesis, with complete but ectopic gullet (x). C. Specimen with two tail poles due to shift of primordium site produced a stentor with unusually large mouthparts, possibly due to the double tail. Primordia far from the posterior end produce no mouthparts (Figs. 47D, and 26c). That the oral-inductive gradient stops short of the posterior pole is indicated in Fig. 5 6a, showing incomplete oral differentiation in a primordium extending too far posteriorly. It is possible, also, that inductive action may be compounded by the presence of multiple posterior ends. When three tails were grafted, double mouthparts were produced in the host (b), and in another case three posterior poles may have been responsible for unusually large mouthparts formed (c). Astomatous oral differen- tiation in large fusion masses may be due to the mutual canceling of oral induction gradients in these random grafts. A similar initial astomatous development in isolated sectors bearing division pri- mordia (Tartar, 1958c) may likewise have been due to the frag- ments at first containing insufficient polar regions, a situation later corrected by regeneration of the posterior Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Tartar, Vance, 1911-. New York, Pergammon Press
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