The morphological aspect of the follicle cells of Styela plicata eggs is described by means of scanning electron microscope investigations. The follicular layer is made of spaced, cylindrical box-like cells which are arranged hexagonally. They adhere to the egg through a complex network of membrane extensions making an overall thin layer on the vitelline coat. The walls of the follicle cells are plentifully provided with microvilli, filopodia and lamellipodia, which allow a connection among the cells. At their apical end lies a large vacuole containing a granule, probably involved in secretion. At insemination the majority of spermatozoa is distributed on the apical membrane of the follicle cells. The membrane often breaks after sperm-egg impact and the granule is therefore displaced. By means of the present investigations it is once again suggested a role played by follicle cells in ascidian eggs at fertilization.