. Protozoo?logy. Protozoa; Protozoa, Pathogenic. 30 GENERAL ORGANIZATION OF THE PROTOZOA tatives of the flagellated and ciliated protozoa, and a characteristic form is found in Euglena viridis and its allies (Fig. 10). Here a definite intranuclear body is surrounded by chromatin granules, and when the cell is ready to divide, this division centre, like a centrosome, divides first and the chromatin elements are separated into two equal groups, each half following one of the centres. In this case, and in some of the infusoria (e. g., Paramecium aurelia [caudatum]) the division centre seems to be
. Protozoo?logy. Protozoa; Protozoa, Pathogenic. 30 GENERAL ORGANIZATION OF THE PROTOZOA tatives of the flagellated and ciliated protozoa, and a characteristic form is found in Euglena viridis and its allies (Fig. 10). Here a definite intranuclear body is surrounded by chromatin granules, and when the cell is ready to divide, this division centre, like a centrosome, divides first and the chromatin elements are separated into two equal groups, each half following one of the centres. In this case, and in some of the infusoria (e. g., Paramecium aurelia [caudatum]) the division centre seems to be formed from a specific substance, and it appears to be a permanent body in the cell, retaining its individuality from generation to generation. Fig. 10. Mitosis in Euglena. (From Wilson after Keuten.) A, preparing for division; the nucleus contains a division centre surrounded by cliromatin granules: B, formation of an intranuclear "central spindle;" C, later anaphase, and D, telophase stage. Much more enlightening, however, are the conditions in the heliozoa. Here, in many cases, there is a central granule in the geometrical centre of the cell, which was early noted by Grenadier ('69) and Schultze and called by the former the " ; The axial filaments of the pseudopodia centre in this granule, which divides like a centrosome prior to division of the cell, while the axial filaments radiate out on all sides like the astral fibers of a mitotic figure. Biit- schli ('92) was the first to compare this body with a centrosome, and the view Avas quickly accepted by cytologists, while the most complete. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Calkins, Gary N. (Gary Nathan), b. 1869. New York and Philadelphia, Lea & Febiger
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