Encyclopedia Britannica (11th ed.) article on Coccidia, an order of parasitic Sporozoa that live inside the cells of vertebrates, molluscs, arthropods and annelids. It covers the history of their discovery, host-cell damage and coccidiosis, the life cycle (schizogony, gametogony, fertilization, sporogony), variations among genera, classification into four families with genera listed, and the debated Cephalopod parasites (Eucoccidium/Aggregata). Two plates of microscopic illustrations and a bibliography by H. M. Woodcock are included. It has no connection to weaving or textiles.