distinct periods in the life cycle which we may call A and B; the individuals of the A period being distinguished by the presence of radiating spicules of MgCO3 in the gelatinous theca; the resolution of period A is simple (fig. 5, 3) and the uninucleate brood-cells are amoebulae (pseudopodiospores) (fig. 5, 4) which grow into the multinucleate B type, with a nonspiculate theca (fig. 5, 5). The resolution of the B type is preceded by rapid multiplication of the nuclei by mitosis (fig. 5, 7), and the uninucleate cells are 2-flagellate zoospores (fig. 5, 9). These pair with zoospores of a different brood to their own (fig. 5, 10) (i.e. they are exogamous gametes); and the fusion cell (fig. 5, 11) so formed is the starting-point of the A type (fig. 5, 12). Brood formation by resolution of a multinucleate individual has been observed or conjectured in Amoeba, &c.
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From Calkin's Protozoa, by permission of the Macmillan Co., New York. |
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Fig. 4.—Bud-fission of Euglypha alveolata. A, passing out of secreted plates to surface of bud. B, bud completely invested; nucleus preparing to divide by mitosis. C, D, later stages. |
A formation of numerous pseudopodiospores within Pelomyxa has been repeatedly described, and these have been seen to conjugate equally, the zygote becoming multinuclear. But the possibility of the alleged reproductive cells being parasites has not yet been fully excluded.
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From The Cambridge Natural History, after Schaudinn, vol. i., Protozoa, by permission of Macmillan & Co. Ltd. |
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Fig. 5.—Trichosphaerium sieboldii. 1, Adult of “A” form; 2, its multiplication by fission and gemmation; 3, resolution into uninucleate amoeboid zoospores; 4, development (from zoospores of “A”) into “B” form (5); 6, its multiplication by fission and gemmation; 7, its resolution after nuclear bipartition into minute 2-flagellate zoospores (or exogametes); 8, liberation of gametes; 9, 10, more highly magnified pairing of gametes of different origin; 11, 12, zygote developing into “A” form. |
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From Eugene Penard, Faune rhizopodique du bassin du Léman. |
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Fig. 6.—A, Euglypha alveolata. 1, Living animal; a, guitar-shaped outline of body, retracted from shell for emission of pseudopods; b, b, reserve plates in body for offspring in next bud-fission; 2, empty shell; 3, round plates; 4, 5, adoral plates with more or less marked denticulations; 6, oval plates; 7, transverse section of shell, showing circle of reserve plates within. B, Sphenoderia lenta. 1, Animal, lateral view; 2, same from above; 3, shell, lateral view; 4, shell, oral view of the pylome; 5, optical section through empty shell and pylome; 6, nucleus; 7, surface view of pylome (dotted lines represent its opposite-side as seen at a lower focus). |
Chlamydophrys stercorea is a small Filose, occurring in the faeces of several mammals, but only forming its characteristic shell outside the body; plastogamic monstrosities are frequent. The nucleus degenerates, and is expelled with some plasm. The chromidia remain inside the shell, and differentiate or aggregate into about eight nuclei; the cell is then resolved into as many 2-flagellate swarmers, which escape as isogamous exogametes. The zygote becomes surrounded by a brown cyst. When
