. The Cambridge natural history. Zoology. MITOSIS OR KARYOKINESIS 29 plasm" or " idioplasm" of relatively great persistence, which gives the cell its own racial qualities.^ The process we have just examined is called " mitosis/' " karyomitosis," or " karyokinesis"; and the nucleus is said to undergo " indirect" division, as compared to " direct" division by mere constriction. In an intermediate mode, common to many Protista, the nuclear wall persists throughout the whole. Fig. 8.—Fission with modified Icaryokiuesis in tlie Filose Ehiz
. The Cambridge natural history. Zoology. MITOSIS OR KARYOKINESIS 29 plasm" or " idioplasm" of relatively great persistence, which gives the cell its own racial qualities.^ The process we have just examined is called " mitosis/' " karyomitosis," or " karyokinesis"; and the nucleus is said to undergo " indirect" division, as compared to " direct" division by mere constriction. In an intermediate mode, common to many Protista, the nuclear wall persists throughout the whole. Fig. 8.—Fission with modified Icaryokiuesis in tlie Filose Ehizopod Eurjlypha. A, out- growth of halt of the cytoplasm, passage of siliceous plates for young shell outwards ; B, completion of shell of second cell, formation of iMfra-nuclear spindle ; C, D, farther stages. (From Wilson, after SchewiakofT.) process, though a spindle is constituted within, and chromosomes are formed and split: the division of the nucleus takes place, however, by simple constriction, as seen in the Filose Ehizopod Eughjpha (Fig. 8). In many Sarcodina and some Sporozoa the nucleus gives off small fragments into the cytoplasm, or is resolved into them; 1 The fact that it is by mitotic division that the undiffei^ntiated germ-cells produce the "differentiated" tissue-cells of the body of the highest animals, is again irreconcilable with such theories, whose chief advocates have been A. Weis- mann and his 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 Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipley, A. E. (Arthur Everett), Sir, 1861-1927. ed. [London, Macmillan and Co. , Limited; New York, The Macmillan Company
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
