Hyaluronidase, a hydrolytic enzyme is an acrosomal content in mammalian sperm. It helps at the time of fertilization during the penetration of sperm into ovum.

Based on the amount of yolk mammalian eggs are alecithal means egg without yolk. Microlecithal eggs are with very little yolk e.g., sea urchin, starfish. On the basis of distribution of yolk telolecithal eggs are those eggs in which the yolk is concentrated towards the vegetal pole and cytoplasm and nucleus lie near the animal pole, e.g., birds and reptiles.

Human eggs are with very little or no yolk at all.