General principles of zoology . FIG. zo.—Cell division according to Rabl. (Skin of Salatnandra maculosa.) Cell Budding. - - Cell multiplication is undoubtedlybrought about chiefly by division, and usually indeed bybinary division. On the surface of the cell there appearsa circular furrow which, deepening, cuts the cell into twoequal parts (Fig. 20).(Division in the narrowersense.) Less frequently ^^^L^^l^^/^icell budding (gemma-tion) takes place, in thecourse of which a largemother-cell cuts off fromitself one or more daugh-ter-cells (Fig. 21). Fora long time there was acontroversy concerningt
General principles of zoology . FIG. zo.—Cell division according to Rabl. (Skin of Salatnandra maculosa.) Cell Budding. - - Cell multiplication is undoubtedlybrought about chiefly by division, and usually indeed bybinary division. On the surface of the cell there appearsa circular furrow which, deepening, cuts the cell into twoequal parts (Fig. 20).(Division in the narrowersense.) Less frequently ^^^L^^l^^/^icell budding (gemma-tion) takes place, in thecourse of which a largemother-cell cuts off fromitself one or more daugh-ter-cells (Fig. 21). Fora long time there was acontroversy concerningthe behavior of tcleus ; some investigators nucleus-affirmed that the nucleus disappeared previous to thedivision, and that in each daughter-cell a nucleus wasformed anew; other investigators believed that the nucleuswas cut in two analogously to the cell. Although the first-. rm FIG. 2I-—Podophrya gemmipara with buds, off and becoming swarmers (by, N, 82 GENERAL PRINCIPLES OF ZOOLOGY, named authors made the best observations, the secondparty was correct in principle. This is explained by thefact that the nucleus in process of division passes into astage in which it absolutely cannot be recognized withoutthe use of suitable and only recently discovered reagents,because in its place is to be seen only an indistinct lighterspot in the protoplasm. This almost complete disappear-ance of the nucleus was entirely overlooked by the zoolo-gists of one party, but on the other hand it was correctlyobserved by the other, though falsely interpreted. For thenucleus, as treatment with acetic or chromic acid shows, isstill present in the light spot, and has only undergone atransformation into the nuclear spindle (Fig. 20). Indirect Nuclear Division, Karyokinesis.—As thename indicates, the nucleus at the critical stage has assumedthe form of a spindle (o
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
