Sur les interactions entre l'axe embryonnaire normal et les formations secondaires produites par la centrifugation de la blastula et de la gastrula chez les Amphibiens

Summary

The complexes of organs induced by centrifugation of Amphibia blastulas or gastrulas interfere with the primary axis of the embryo: (a) explantates of centrifugated ectoblast are always poorer in differentiation than the same ectoblast leftin situ; (b) the complexes arising in the ventral part of the embryo have the tendency to elongate parallel to the main axis of the embryo and become connected with the head of the primary embryo; (c) grafts made on Axolotl eggs show that, when the reaction is poor, it cannot express itself except in cases of close contact with the normal organizer; (d) reciprocally, implants of strongly reacting centrifugated ectoblast placed on the ventral part of a normal gastrula of Pleurodeles induce modifications of the primary organs, viz. the transformation of the first somites into chorda.

These facts lead to the conclusion that quantitative factors—and not qualitative—are effective in the differentiation of the embryo.