. Protozoo?logy. Protozoa; Protozoa, Pathogenic. GENERAL MORPHOLOGY 19 or a Bursaria truncatella, reaching the size of 2 mm. (one-twelfth of an inch), while the parasitic gregarine Porospoi-a gicjaniea of the lobster's gut attains the length of 16 mm., or two-thirds of an inch. Unlike the majority of bacteria, the size of any given species of protozoa often varies within wide limits, and this in the same environ- ment. The reasons for this difference are numerous, sometimes it is due to starvation, sometimes to developmental condition, and some- times to the variations in vitality at different
. Protozoo?logy. Protozoa; Protozoa, Pathogenic. GENERAL MORPHOLOGY 19 or a Bursaria truncatella, reaching the size of 2 mm. (one-twelfth of an inch), while the parasitic gregarine Porospoi-a gicjaniea of the lobster's gut attains the length of 16 mm., or two-thirds of an inch. Unlike the majority of bacteria, the size of any given species of protozoa often varies within wide limits, and this in the same environ- ment. The reasons for this difference are numerous, sometimes it is due to starvation, sometimes to developmental condition, and some- times to the variations in vitality at different periods in the life history. Thus, two cells from the same culture of dileptus species may be mis- taken for different species, the difference between them being so great, Fig. 2. Dileptus, sp. Two sister cells. A, normal individual with macronucleus in form of scattered chromatin granules (chromidia); B, individual starved for several days. From photographs taken with same magnification. and due solely to the lack of food in one case (Fig. 2). This divergence in size is particularly noticeable in the parasitic forms, where many factors influence the development of the cell. Many forms of protozoa, especially the flagellated types, have acquired the habit of association into colonies, and with such associa- tion have gained the economy which comes from division of labor, so that here in the colony forms may be found the first step in the differentiation of cell aggregates and the nearest approach of protozoa to the metazoa. Such colonies have been designated according to their mode of formation, gregaloid, spheroid, arboroid, and catenoid. 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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