AN EXPERIMENTAL STUDY OF CONCRESCENCE IN THE EMBRYO OF CRYPTOBRANCHUS ALLEGHENIENSIS

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Abstract
By the method of vital staining the following facts concerning the formation of the embryo of Cryptobranchus were established: (1) A band of cells occupying the lateral and ventral parts of the equatorial region of the late blastula, during gastrulation comes to occupy the corresponding parts of the margin of the yolk plug, and converges on the site of the closing blastopore. (2) During gastrulation there is a confluence of material lying in the region of the dorsal lip of the blastopore: in connection with the process of overgrowth and in-turning of the dorsal lip of the blastopore, this material shifts from either side toward the median line. (3) The movement of the neural folds is a movement of translation, not a mere wave movement; the neural folds include material originally situated at least 90° apart, which is thus brought into apposition in the median line. The bearing of these facts on the theory of concrescence is discussed.

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