Basic nature of sexual reproduction

High-powered microscopic shots are used to illustrate the principle that sexual reproduction in simple and complex plants and animals always involves the production and the union of gametes; exemplifies the details of fusion by showing the union of the sperm and egg of a salamander. By means of time-lapse photography, follows the steps in the life cycle of the salamander. Explains that sexual reproduction provides both for the continuation of life and for the variations which benefit man.