Abstract
This paper describes the outlines of both spermatogenesis and oogenesis observed in the pearl-oyster (Pteria martensii). The specimens for material were collected in Ago Bay, Mie Prefecture, during a period from the beginning of May to the beginning of June. The gonads were fixed with weak and strong Flemming's solutions and Lo Bianco's mixture. It was found that the ripening of both testes and ovaries took place at the same time in the individuals of the same age. The primary spermatocytes showed at metaphase 18 bivalents of small spherical shape. There were again 18 chromosomes in the secondary spermatocytes. In both the first and second divisions, the chromosomes separate into equal halves, showing no element characterized by a particular structure.
The occurrence of testis-ova was rather common in the testes, and the ovaries frequently showed the presence of many spermatozoa.
