Mass Coral spawning is now thoroughly documented on film. What is less well know is the precise process of gamete release from individual coral polyps. the package seen being released in this series of shots of Acropora spawning, is in reality a tightly bundled ball, consisting of maybe five or six eggs, bound together by a glutinous matrix of sperm cells. When the product rises to the surface, takes up water, softens and breaks apart, millions of sperm swim free while the ciliated eggs slowly roll around close to the surface film awaiting fertilisation by sperm from other coral heads, before developing into the more mobile and streamlined ciliated planulae. It is these that will be ultimately responsible for settlement, cementing to a coralline substrate, and initial formation of the calcareous skeleton upon which the new colony will be founded.