Surface topography of isolated gastrula ectoderm of Triturus vulgaris.

The surface topography of the outer cell layer of the two-layered gastrula ectoderm of Triturus vulgaris resembles that of the other amphibians: the cells are tightly packed and devoid of pseudopodia. The cells of the inner layer are spherical and interconnected with pseudopodia of various lengths. After excision of the ectoderm the peripheral cells of the outer layer elongate perpendicularly to the edge of the explant, while the number of pseudopodia on the inner layer greatly increases. The results show that the curling-up of the explant and formation of a sphere results from locomotor activity of the cells in both layers.