The number of primordial germ cells (PGC) in albino tadpoles of Xenopus is significantly decreased as compared with that of the wild‐type. Whether the decreased number of PGC is caused by the presumptive PGC (pPGC) themselves or the micro‐environment surrounding those cells in the albino, or both was investigated in the present study. [³H]thymidine‐labeled pPGC of wild‐type and albino were implanted into unlabeled, host neurulae of wild‐type br albino and wild‐type, respectively. Labeled PGC in the genital ridges of experimental tadpoles were examined by autoradiography. There were no significant differences in the proportion of tadpoles with labeled PGC and in the average number of those PGC between the albino and wild‐type tadpoles, into which wild‐type pPGC had been implanted. The proportion in wild‐type tadpoles with albino pPGC was much lower than that in wild‐type tadpoles with wild‐type pPGC. These results suggest that the pPGC of the albino and not the micro‐environment are responsible for the decreased number of PGC.