Abstract: In 1997， the ultrastructure of mussel ovary was observed，the oogonium，oocyte I and previtellogenic oocyte have the similar ultrastructure. They all consist of nucleus with a nucleolus，rough endoplasmic reticulum， sphere-like mitochondria and free ribosome, etc. During the vitellogenesis，the volume of oocyte becomes larger and larger, because there are many yolk granules and lipid droplet in the plasm of oocyte. The oocyte have microvilli on their surface with which the oocyte will mature soon. The yolk body is made up of mutual resource, but most of yolk is get from other tissues.
1999, Vol. 14 
