Cellular Interactions in Cell Differentiation

It is of some interest, in connexion with the problem of cellular interactions, to view the affinities between different tissues in various stages of development. The problem has been extensively investigated by Holtfreter in the early stages of the amphibian egg. Professor P. Weiss has briefly reported on the stimulating observations made by Chiakulas (1952) on grafts of epithelia from various sources to the skin of larval amphibians. I have performed experiments which bear some analogies to the last-mentioned ones by confronting side by side in situ layers of heterogeneous tissues, which in normal development form distinct constituents of one anatomical region, namely the eye region. Pieces of tissues of various extent were mechanically removed from the eye-forming region of chick embryos of from 2 to 30 somites, and more or less wide gaps created.