preformation: a theory (popular in the 18th century and now discredited) that an individual develops by simple enlargement of a tiny fully formed organism (a homunculus) that exists in the germ cell
theory: a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena
sprinkler system: a system for extinguishing fires; water from a network of overhead pipes is released through nozzles that open automatically with the rise in temperature