Contribution to the Study of Germ-cells in the Anura

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Abstract
Shortly after fertilization of the egg of R. temporaria there arise, near the vegetal pole, small islets of specifically stainable cytoplasm that eventually become included in cells lying in the blastocoel floor. From this time forward the special cytoplasm becomes increasingly difficult to identify with the cytological techniques used, but not until it is possible to confirm that the cells in question are primordial germ-cells. Thus the findings of Bounoure (1934) for this species are confirmed and extended. This germinal cytoplasm has also been found in the eggs and embryos of X. laevis and B. bufo, but, rather surprisingly, not in R. esculenta. The germ-plasm is, at first, rich in pentosenucleic acid (PNA) but loses this property shortly after an intracellular change in its position which occurs in the earliest stages of gastrulation. Examination of parthenogenetically activated eggs reveals that germinal cytoplasm can be formed in the absence of sperm.