Further Experiments on the Transplantation of Neural Crest (Mesectoderm) in Amphibians.

Abstract

In previous experiments 1 the author has shown that when mesectoderm was excised in the cranial regions of early stages of embryos of Amblystoma punctatum deficiencies were produced in the branchial skeleton, Meckel's cartilage, palatoquadrate bar, anterior trabeculae and loose mesenchyme in the head. It was further found 2 that when groups of mesectoderm cells were transplanted to new positions on the side of the body they differentiated into cartilages in the presence of the strange mesentoderm (mesoderm) of the somites and in the absence of mesentoderm of the visceral arches.

A similar study has been extended to the Anurans. In Rana palustris the author reported³ a migration of bands of mesectoderm over the mesentoderm of the visceral arches from the dorsal part of the cranial portion of the neural folds similar to the condition found in Amblystoma. The migration begins before the closure of the neural folds—an earlier stage than in Amblystoma. It was found in those studies³ in Rana that when the mesectoderm was removed deficiencies were produced in the visceral skeleton on the operated side.

Further tests of the ability of the mesectoderm to form cartilages in the anurans have been made by a series of transplantation experiments upon early stages of Rana palwtris in which one or more bands of these cells have been placed in new positions on the side of the boy. The relative growth of the bands of mesectoderm at the time of operation is shown in Fig. 1. This is just before the closure of the neural folds and seems to be the most feasible time for removing the mesectoderm for transplantation. Very soon after this stage the mesectoderm over the branchial region splits into 4 bands, 1 for each branchial arch.