Investigations of the Germ-plasm in Relation to Nuclear Transplantation

Primordial germ-cells in R. pipiens mid-blastula and early gastrula stages were detected in serial sections, because these cells contained a stainable component, the germ-plasm. Their location was of prime interest in determining whether or not the nuclei of primordial germ-cells had been used in previous transplantation studies (King et al., 1959; Briggs & King, 1960). In the mid-blastula and early gastrula stages the primordial germ-cells were confined to the vegetal hemisphere. The majority of these cells was situated in the upper-third of the vegetal hemisphere. An intracellular displacement of the germ-plasm occurred between mid-blastula and early gastrula stages. The number and location of the primordial germ-cells suggest that only in rare cases could a nucleus from one of these cells have been transplanted in the previous studies, and such cases would probably have been undetectable. What appears most significant is that nuclei derived from cells not containing germ-plasm are capable of giving rise to larvae whose gonads contain numerous auxocytes.