. The cell; outlines of general anatomy and physiology. in two species of Desmidiaceae : the Clos-terium and Cos murium. Two Closterium cells, which are shaped somewhat like bentsickles, lie lengthwise against each other, being kept in contactby a gelatinous secretion ; each then develops a protuberance nearits centre. The two protuberances come closely into contact andfuse, whilst the wall separating them dissolves, to form a conju-gation canal common to both. Here all the protoplasm from boththe conjugating Closterium cells gradually collects, and, detachingitself from the old cell membrane,
. The cell; outlines of general anatomy and physiology. in two species of Desmidiaceae : the Clos-terium and Cos murium. Two Closterium cells, which are shaped somewhat like bentsickles, lie lengthwise against each other, being kept in contactby a gelatinous secretion ; each then develops a protuberance nearits centre. The two protuberances come closely into contact andfuse, whilst the wall separating them dissolves, to form a conju-gation canal common to both. Here all the protoplasm from boththe conjugating Closterium cells gradually collects, and, detachingitself from the old cell membrane, fuses toform a single globular body, which finallybecomes surrounded by a membrane of itsown. This zygospore or zygote, which has beenproduced by the fusion of two similar indi-viduals, now passes through a resting stage,which lasts for several months (Fig. 150). fig. iso. — Zygote ofIt contains two nuclei, which were derived Clo«ter»«m, just before . germination. (After Kle- trom the two cells, and which remain apart bahn, pi. xin., Fig. 3.). 280 THE CELL during the whole of the resting period. It is not until thespring, when a new vegetative period recommences, that thenuclei come close together, and fuse to form a germinal nucleus. At this period the zygote, which is surrounded by a delicatemembrane, makes its way through the old cellulose wall, whilstits germinal nucleus transforms itself into a large spindle, ofsomewhat unusual appearance (Fig. 151 I). This divides intotwo half-spindles (Fig. 151 II), which, however, do not enter intothe resting condition, but immediately prepare to divide again J. n.
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Keywords: ., bookcentury1800, bookdecade1890, bookidcelloutlines, bookyear1895
