Archive image from page 93 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar_0 Year: 1920 78 CYTOLOGY CHAP. of the early cleavage stages are double, each portion being the direct descendant of one of the gamete nuclei. Each constituent of such a double nucleus is called a gonomere. In prophase each gonomere forms its chromosomes separately from the other. The two groups of chromosomes thus formed are usually indistinguishable from one another after the break-down of the nuclear membrane, but in telophase they become recogni
Archive image from page 93 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar_0 Year: 1920 78 CYTOLOGY CHAP. of the early cleavage stages are double, each portion being the direct descendant of one of the gamete nuclei. Each constituent of such a double nucleus is called a gonomere. In prophase each gonomere forms its chromosomes separately from the other. The two groups of chromosomes thus formed are usually indistinguishable from one another after the break-down of the nuclear membrane, but in telophase they become recognizable again owing to the fact that the group of chromosomes derived from each gonomere again forms a nucleus distinct from, though closely applied to, that formed by the other group. Occasionally, however, the two groups are distinct during metaphase and anaphase as well (Fig. 35, A). In later cleavage stages the chromatin derived from the two gamete nuclei gradually mingles more and more, and double nuclei become consequently rarer. In Cyclops brevicomis double and bilobed Gonomery in Cyclops ttrcnuus. (After Riickert, , 1895.) A, 2-4-cell stage, the groups of chromo- somes derived from 6 and 9 gametes quite separate; B, 4-cell stage. In the nucleus in prophase the two groups of chromosomes are seen. C, 32-cell stage. Gonomeres indicated in most of the nuclei. nuclei are still common in the 64-cell stage, and in later stages bilobed nuclei with a nucleolus in each lobe are still to be found, as well as spherical nuclei with two symmetrically placed nucleoli, which Hacker interprets as the last remaining indication of gonomery. In the germ-track (see p. 79) evidences of gonomery can be found at a much later stage of development than in the somatic cells (Hacker, 1903). A remarkable instance of gonomery is to be found in the Protozoan, Amoeba diploidea (Nagler, 1909). This animal possesses two nuclei, in close apposition to one another (Fig. 36), exactly like the double
Size: 2343px × 854px
Photo credit: © Actep Burstov / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: 1920, agar_w_e_wilfred_eade_1882_1951, archive, book, bookauthor, bookdecade, bookpublisher, booksponsor, booksubject, bookyear, boston_library_consortium_member_libraries, cells, drawing, historical, history, illustration, image, london_macmillan_and_co_limited, page, picture, print, reference, vintage, zimmermann_a_albrecht_b_1860
