Eggs having yolk in their centre of cytoplasm, are called centrolecithal. It is found in some insects and Hydrozoa. In microlecithal eggs, the amount of yolk is so little that it is found scattered almost uniformaly throughout the egg cytoplasm. Such eggs with evenly distributed yolk in ooplasm is called isolecithal. Microlecithal eggs are with very small amount of yolk and telolecithal eggs have a polarised distribution of yolk.