Heavy infestations with the intestinal parasite Proctoeces sp. were detected in the bar-tail flathead Platycephalus indicus collected from Alataka harbor, Suez Gulf, Egypt. Different developmental stages of vitellocyte and oocyte maturations of this digenean parasite were studied using transmission electron microscopy. The vitelline masses are covered with a delicate fibrous layer and enclosed with segregated circular muscle bundles. The first stage (S1) of vitellocytes maturation is distinguished by a large centrally located oval nucleus and abundant mitochondria and free ribosomes fixed at a perinuclear reside. The second stage(S 2) of vitellocyte maturation has greater cytoplasmic volume, Golgi vesicles, granular endoplasmic reticulum and the vitelline globules became more electron-dense. The third stage (S 3) is characterized by an oval nucleus, shell globules with different sizes aggregated in clusters, electron-lucent lipid droplets and osmiophilic glycogen .The cytoplasm of mature vitellocytes (S 4) was gradually degraded, involving analogous sacs of granular endoplasmic reticulum situated at the peripheral and perinuclear regions, glycogen granules, lipid droplets and packed larger globule clusters. During vitellocyte developmental stages, the nucleo-cytoplasmic ratio decreased while the synthetic activities increased. Detailed ultrastructural characteristics of four different developmental stages of oocyte maturation were briefly described.