An electron microscopic study of the vitelline follicles of
Metamicrocotyla macracantha (Alexander, 1954) Koratha,1955 showed
that they are composed of cells in different stages of development. The
immature cells have a large nucleus, nucleolus, cytoplasm with free
ribosomes and few mitochondria. The developing vitelline cells present
granules which are small in the early stages, increasing with maturity. The
mature cells have an extensive granular endoplasmic reticulum and droplets
of shell-protein; with maturation, clusters of shell protein and yolk
bodies are formed and released in the ciliated vitelline ducts. Vitelline
development is continuous and all of the cellular stages involved can be
found in each follicle. {P}
