As maturation of vitelline cells continues shell globule clusters become
packed with lipid droplets and glycogen. The role of these inclusions
is very important as a source of energy for developing embryo.
In spite of the great similarity observed in the embryonic development
of diphylobothriideans, caryophyllideans and spathebothriideans, their
vitellocytes differ in the chemical compounds and amount of their
nutritive reserves.