Differential Oxidation and Reduction of Indicators in Reconstitution of Hydra and a Planarian

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Abstract
Alterations of oxidation-reduction indicator patterns in reconstitution of isolated pieces of hydra and a planarian are in general very similar, except as regards certain features associated with entodermal differences in the 2 forms. In isolated pieces an increase in rate of oxidation and reduction of indicators, greater at distal or anterior, than at proximal or posterior ends, follows section immediately as a direct effect of injury. This is replaced or followed by a gradient of increased rate, extending with a decrement from the distal or anterior cut end for a certain distance. At the proximal or posterior cut end there is much less evidence of activation and a shorter and less sharply defined gradient. The differences at the 2 ends of pieces are features, first, of the longitudinal gradient pattern of the parent animal and of the piece as a part of it, and 2d, at the distal or anterior end, of the isolation from the dominance of more distal or anterior regions. The alteration at the distal or anterior end constitutes imposition of a new longitudinal gradient pattern on the piece. This precedes any evidence of morphogenesis and becomes the locus of development of distal or anterior regions of the new individual. Reconstitution of proximal or posterior parts is determined by relation to other parts of the piece and involves only slight change in oxidation-reduction patterns. In the intact planarian the entodermal oxidation pattern is the reverse of the reduction pattern. In reconstitution the entodermal patterns undergo alterations corresponding to the alterations in regions of the body determined in different parts of the piece by reconstitution. In pieces from different body levels different parts of the ento-derm of the parent animal attain the oxidation-reduction pattern which is characteristic of an entire individual. The cephalic ganglionic region reduces methylene blue more rapidly than other parts of the planarian body and reduction progresses posteropetally from it along the nerve cords and the region between them; at any particular body level it is more rapid than in other parts at the same level.

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