Tissue degeneration: an electron microscopic study of the pronephros of Rana temporaria.

The structure of the non-degenerate and degenerating pronephros, of larval Rana temporaria, at different stages of the metamorphic cycle, was examined by electron microscopy. Extra-renal cellular components in the circulation were likewise investigated, and particular consideration was given to their relationships with the pronephric tubules whose regression would seem to be bound up with them. The activity of lysosomes in pronephric tubule degeneration suggests that they are an important component of the degeneration process, which probably embraces autolysis and phagocytosis.