[Ultrastructural study on the vitelline cells of Pagumogonimus skrjabini]

This paper reported on the ultrastructure of the developing vitelline cells of Pagumogonimus skrjabini by using transmission electron microscope. The vitelline glands were isolated under dissecting microscope from the adult worm of P. skrjabini before 2.5% glutaraldehyde fixation. Four developmental stages of the vitelline cell were described. In stage 1. the nucleus contained many heterochoromatins. The mitochondria, ribosomal complex, rough endoplasmic reticulum and glycogen granules were observed in the cytoplasm. In stage 2. the typical characteristic of the developing cell was the grouping together of the vitelline globules. The junctional complexes were seen between the vitelline cells. In stage 3, that represented the initial stage of vitelline droplet formation, the vitelline cells were filled with rough endoplasmic reticulum. The immature vitelline cells included stage 1-3. In stage 4. the mature cells were divided into two phases. In the early phase of stage 4, the cytoplasm contained abundant glycogen granules, lipid droplets and a lot of ribosomal complexes and rough endoplasmic reticulum, while in the later phase part of the perinuclear cisterna showed vacuolization. The cytoplasm contained a large number of glycogen granules and the vitelline droplets were distributed on the inner border of the cell. In the developing egg, the vitelline granules adhered to the egg-shell.