Histology Studies on the Female Gonad of Paphia (Paratapes ) undulta (Born)

The histology of female gonad of Paphia (Paratapes) undulata (Born) was studied with light microscope. The female gonad is composed of blanch ovary and oviduct. The ovary consists of great number of branched genital canal and capsules. The histology of ovary is made up of a thin wall which consists of connective tissue and thin layer muscle and endogenic epithelium that grow into germinative zone. The wall extends into ovary and divides it into many small parts, and the germinative zone produces oogonium developing into other female germ cells. According to the size and shape of cells, nuclei and nucleoli, and the vitelline accumulation, the oogenesis can be divided into seven stages: oogonium stage, oocyte I stage, oocyte Ⅱ stage, early vitellogenesis stage, middle vitellogenesis stage, post vitellogenesis stage and mature oocyte stage. In the early and middle developing oocytes, some nucleolar substance, which is considered to be probably related to the formation of yolk within the oocyte, enters into nucleus and cytoplasm. The nucleolus of late developing oocytes and ripe eggs becomes amphinucleous. This paper reports on the results of a study on the retartded egg and degenerated egg in the ovary of the clam. The ovary has a seasonal developing change.