Morphology, biometry and taxonomic position of two peritrich ciliate Protozoa found in activated sludge.

The morphology of two sessile peritrich species taken from a plant for the processing of activated sludge is described. One of these species, having a non-contractile, branched peduncle, belongs to the genus, Heteropolaria, and the other having a single, contractile stalk, is a member of the genus Vorticella. A statistical and biometric study is made of their morphological characteristics, and the taxonomic position of both ciliates is discussed.