SYNOPSIS. Miamiensis avidus n. g., n. sp., a marine facultative parasite, is described. Morphological studies were made on specimens treated with the Chatton‐Lwoff silver impregnation technique and living material was examined with phase microscopy. Particular attention was given the infraciliature of the buccal apparatus and its importance to generic assignment in the order Hymenostomatida.

SYNOPSIS. A comparative study of five species of Tetrahymena, including thirteen strains, was made to ascertain their ability to act as facultative parasites. A variety of experimental hosts, including both vertebrates and invertebrates, were inoculated with axenic cultures of protozoa. Infections were numerous in both larval and adult insects. Tissues of living vertebrates were invaded by one species of Tetrahymena through artificially produced wounds.

SYNOPSIS. A new family (Pseudocohnilembidae) of hymenostome ciliates is described based primarily upon the pattern of the buccal infraciliature which consists of two parallel rows of kinetosomes, nearly equal in length, representing the bases of two large membranes, and of argentophilic fibrils arranged in a more or less uniform design in the buccal cavity. A new genus (Pseudocohnilembus) with three species (one from Great Salt Lake, Utah, and two from the Atlantic coast) is described. These organisms bear superficial resemblance to Cohnilembus; an analysis of the buccal infraciliature of Pseudocohnilembus is presented, including a discussion of and comparison with that of Cohnilembus.