Cytological Studies on Pelomyxa carolinensis with Special Reference to the Mitochondria*

Abstract

SUMMARY. The mitochondria of living, unstained Pelomyxa carolinensis are homogeneous, nonrefractile bodies and occur as spheres, short rods, dumbbell forms or elongated rods. All forms are distributed uniformly throughout the cytoplasm, except for characteristic accumulations around the contractile vacuoles and small food vacuoles. Mitochondria were never observed within food vacuoles, nor in intimate contact with large food vacuoles containing recently ingested paramecia.Aqueous solutions (1:200,000) of Janus green B, Janus blue, and Janus red stained the mitochondria. After 12 hours in Janus green B and Janus blue or 24 hours in Janus red, the mitochondrion appears as a differentiated structure with the stain localized in eccentric granules or crescentic areas. Aqueous solutions of Janus black (1:200,000), amethyst violet (1:200,000) and Rhodamine B (1:50,000) stained only food vacuoles within the organisms.Dumbbell forms and elongated rods, often interpreted as division stages, were continuously observed in the living organism. These observations failed to reveal any division process.Sectioned material was prepared from animals fixed in Champy's, Regaud's, Altmann's and Helly's fluids, as well as in a fixative composed of equal parts of 1% (w/v) chromic acid and 2% (w/v) osmium tetroxide. Excellent results were obtained with Champy and chrom‐osmic fixation, while the other fixatives proved to be of little value.