Stages 3 and 4 of vitellogenesis in C. metoecus. (5) General observation of a vitelline cell at the third stage of maturation. Scale bar = 1 μm. (6) The third stage of vitellocyte maturation showing the coalescence of single shell globules into a cluster surrounded by a membrane. Scale bar = 1 μm. (7) Cytoplasm of a vitelline cell at the third stage of maturation containing shell globule cluster and saturated lipid droplets, surrounded by glycogen granules. Stained according to the Thiéry method. Scale bar = 1 μm. (8) Electron micrograph of a vitelline cell at the fourth stage of maturation filled with shell globule clusters and lipid droplets. Scale bar = 1 μm. G: glycogen particle; GER: granular endoplasmic reticulum; L: lipid droplet; M: mitochondrion; N: nucleus; Nl: nucleolus; SG: shell globule; SGC: shell globule cluster.