. Pathogenic micro-organisms. A text-book of microbiology for physicians and students of medicine. (Based upon Williams' Bacteriology). Bacteriology; Pathogenic bacteria. CILIOPHORA 453 cession to form eight nuclei, of which four enlarge to become macronuclei, one remains as a micronucleus and three disin- tegrate and disappear. The one micronucleus then divides by mitosis and the cell divides to form two paramaecia, each contain- ing one micronucleus and two ^ macronuclei. The next division gives rise to cells containing the normal number of nuclei, one micronucleus and one macro- nucleus. Th
. Pathogenic micro-organisms. A text-book of microbiology for physicians and students of medicine. (Based upon Williams' Bacteriology). Bacteriology; Pathogenic bacteria. CILIOPHORA 453 cession to form eight nuclei, of which four enlarge to become macronuclei, one remains as a micronucleus and three disin- tegrate and disappear. The one micronucleus then divides by mitosis and the cell divides to form two paramaecia, each contain- ing one micronucleus and two ^ macronuclei. The next division gives rise to cells containing the normal number of nuclei, one micronucleus and one macro- nucleus. The paramaecia are lagre sapro- phytic organisms, easily kept under cultivation in the laboratory, and they have been very extensively studied. Many conceptions founded upon these studies are considered to have a broad bear- ing upon the physiology of all living cells. For example Jen- nings^ has found that conju- gation serves two purposes, (i) to provide chemical stimulation of cell division and (2) to insure va- riety in the descendants. The variety in the descendants is a result of the exchange of nuclear material. Calkins^ has dis- covered a specialization of function in paramaecium in respect to conjugation and concludes that in some of the descendants of an px-conjugant the ability to conjugate is in abeyance, thus suggesting a resemblance to the somatic cells of a metazoon, . while other descendants retain this function and are therefore analogous to the germ cells of a metazoon. Three other species of Paramecium are recognized, namely, P aurelia. P. bursaria and P. putrinum. ' Harvey Lectures, 1911-12, pp. 256-276. "iProc. Soc. Exp. Biol, and Med., 1913, Vol. X„pp. Fig. 217.—Paramaecia drawn at the same magnification. A, Para- mcecium caudatum. B. Paramaciuni putrinum. (From Doflein after Sche- wiakoff).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance
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