SYNOPSIS OF GROUPS.
A. Protozoa. Unicellular animals, dissociated, or associated in simple, loose colonies of similar organisms. Many have an exoskeleton of lime, flint, or other material. Reproduction by fission and by temporary or permanent conjugation.
B. Metazoa. Multicellular animals, consisting of a large number of cells associated together to form single, complex individuals. The cells of an individual are usually differentiated into several kinds performing special functions. Reproduction in the higher forms is sexual; in the lower forms it is often by budding as well as sexual.