The Transition of Peritoneal Epithelial Cells into Germ Cells in some Amphibia Anura, especially in Rana temporaria

Abstract

(1)Germ-thickenings in the peritoneal epithelium surrounding the ovary do not appear in winter.(2) In early spring differentiating areas appear in the peritoneal epithelium. Followed out, these thickenings are found to become ovariform germ pockets containing newly formed germ cells in all stages.(3) The intermediate stages between peritoneal cell and germ cell consist primarily in the elimination of a greater part of the chromatic matter of the nucleus, in the appearance of a granular zone in the cytoplasm which becomes totally granular and stains more heavily than before, and finally in the appearance of several nucleoli subsequent upon a loss of the regular shape of the nucleus.(4) Intermediate stages have been looked for and found in other Amphibian ovaries.(5) Thickenings containing many thousands of germ cells and larger than the entire ovary of a lately metamorphosed frog have been found, especially in May.(6) Reasons are given why the cells composing the germ thickenings in the ovary are not to be considered stored-up germ cells.