. The cell in development and inheritance. Cells; Cells. B pronucleus (Fig. 82, C-H). Each animal now contains a cleavage- nucleus equally derived from both the conjugating animals, and the latter soon separate. The cleavage-nucleus in each divides three times successively, and of the eight resulting bodies four become macronuclei and four micronuclei (Fig. 82, H-K). By two suc- ceeding fissions the four macronuclei are then distributed, one to each of the four resulting individuals. In some other species the micro- nuclei are equally dis- tributed in like man- ner, but in P. caitda- tiim the
. The cell in development and inheritance. Cells; Cells. B pronucleus (Fig. 82, C-H). Each animal now contains a cleavage- nucleus equally derived from both the conjugating animals, and the latter soon separate. The cleavage-nucleus in each divides three times successively, and of the eight resulting bodies four become macronuclei and four micronuclei (Fig. 82, H-K). By two suc- ceeding fissions the four macronuclei are then distributed, one to each of the four resulting individuals. In some other species the micro- nuclei are equally dis- tributed in like man- ner, but in P. caitda- tiim the process is more complicated, since three of them degenerate, and the fourth divides twice to produce four new micronuclei. In either case at the close of the process each of the conju- gating individuals has given rise to four descendants, each containing a macro- nucleus and micro- nucleus derived from the cleavage-nucleus. From this time for- ward fission follows fission in the usual manner, both nuclei dividing at each fis- sion, until, after many generations, conjuga- tion recurs. Essentially similar facts have been observed by Richard Hertwig and Maupas in a large number of forms. In cases of permanent conjugation, as in Vorticella, where a smaller microgameie unites with a larger niacrogaviete, the process is essentially the same, though the details are still more complex. Here the germ-nucleus derived from each gamete is in the macrogamete one-fourth and in the microgam- ete one-eighth of the original micronucleus (Fig. 83). Each germ- nucleus divides into two, as usual, but one of the products of each degenerates, and the two remaining pronuclei conjugate to form a 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 Wilson, Edmund B. (Edmund Beecher), 1856-1939. New York : The Macmilla
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectcells, bookyear1896
