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Not AvailableUltrastructural features of the ovary as well as oogenesis were examined in the variable abalone Haliotis varia with the help of transmission electron microscopy. Based on the ultrastructure, the female germ cells were divided into 5 stages; oogonia, pre-vitellogenic, early vitellogenic, late vitellogenic and mature oocytes. Oogonia were supported by follicle cells that lined up the inner walls of the ovary. Vitellogenesis in H. varia commenced at about 50 μm oocyte diameter, with a major contribution by the autosynthetic pathway. Lipid droplets and protein yolk granules, measuring 2.3 ± 0.2 and 2.5 ± 0.3 μm, respectively, were observed in late vitellogenic and mature oocytes. Vitellogenic oocytes were encircled by a vitelline envelope consisting of a single layer of about 2.3 μm thickness. Numerous microvilli were embedded in the vitelline envelope. Cytoplasmic inclusions such as cortical granules, lipid droplets, mitochondria and yolk granules constituted the fundamental components of the mature oocyte. The cortical granules were arranged beneath the oolemma at the cortex of the oocyte. Oocyte degeneration in H. varia was observed in all stages of oocyte development, except in oogonial cells and pre-vitellogenic oocytesNot Availabl