Yolk Formation in Oocytes of Patella coerulea L. and Aplysia depilans L. as observed in the Electron Microscope

Abstract

ELECTRON microscope research on vitellogenesis has so far been mainly concerned with the identification of the precursors, or cellular constituents, from which the yolk formation begins1–5. The origin of the yolk and further stages in its formation in oocytes of Patella coerulea and Aplysia depilans are described here. Small fragments of the female gonads were fixed in a 1 per cent solution of osmium tetroxide at pH = 7.4 for 1 hr. Other technical details are reported in a previous paper6. Preparations and observations were made at the Centre for Electron Microscopy at the University of Padua with a Siemens Elmiskop Ia apparatus.