Didinium is primitive, barrel-shaped ciliate characterized by 2 bands of cilia. They prefer to feed upon Paramecium. They possess a toxin, which is released upon contact with prey, and it serves to kill and paralyze its victim. Simultaneously, the toxin causes the Paramecium to lose its cilia. Paramecium are widely distributed throughout freshwater habitats, where they feed upon bacteria. There are many different species of Paramecium. X1400.