An examination into the phenomenon of granulation, in mu particles of stock 540 Paramecium aurelia.

Mu particles are endosymbionts found in the cytoplasm of Paratnecium aurelia (Sonneborn, 1959; Preer, 1967; Beale, Jurand & Preer, 1969; Jurand & Selman, 1969). They are responsible for the phenomenon of mate-killing (Siegel, 1954; Beale, 1957) but can be removed from stock 540 paramecia by a variety of methods (Beale, 1957; Gibson & Beale, 1962; Franklin, 1973). The technique used by Beale (1957) involves growing the paramecia at 37 °C. During a series of experiments designed to examine the cause of particle loss (Franklin, 1971) it became apparent that mu, in paramecia destined to become mu-free after such treatment, became granulated during incubation at 37 °C. This phenomenon had not been reported previously and so a detailed examination into the structure and formation of the granules was carried out.