. Cytology, with special reference to the metazoan nucleus. Cells. 4^ CYTOLOGY CHAP. This absence of a bouquet is not, however, characteristic of insects in general, for it is a conspicuous feature in many species. Diplotene nuclei (I) show us that each pachytene thread proceeds to split into a pair in the same manner as we saw in the two forms already. Fig. 17. The formation of the meiotic bivalents in certain insects. (After Wilson, , 1912.) A-J, Oncopeltus ; K, Anax ; L-N, Protenor. A, B, spermatogonial telophase; C, emergence of massive chromatin bodies in spermatocyte I. ; D, E, eac
. Cytology, with special reference to the metazoan nucleus. Cells. 4^ CYTOLOGY CHAP. This absence of a bouquet is not, however, characteristic of insects in general, for it is a conspicuous feature in many species. Diplotene nuclei (I) show us that each pachytene thread proceeds to split into a pair in the same manner as we saw in the two forms already. Fig. 17. The formation of the meiotic bivalents in certain insects. (After Wilson, , 1912.) A-J, Oncopeltus ; K, Anax ; L-N, Protenor. A, B, spermatogonial telophase; C, emergence of massive chromatin bodies in spermatocyte I. ; D, E, each chromatin body (with the exception of two, the sex chromosomes) is giving rise to a single coiled thread; F, the coiled threads of E have given rise to the leptotene nucleus; G, synizesis; H, the pachytene stage ; the large, faintly stained body in this figure, and in figures I, J, is the plasmosome ; I, diplotene stage ; J, " confused stage " ; K, three contiguous cells showing the evolution of the coiled threads from the massive bodies ; L, M, N, evolution of the bivalent rings from the confused stage. described. Instead, however, of these pairs condensing progressively into the definitive bivalents of metaphase L, the early diplotene stage is immediately followed by one which Wilson calls the " confused stage " (J), in which the double chromosomes lose their visible identity and become merged into a vague, lightly staining reticulum. From this. 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 Agar, W. E. (Wilfred Eade), 1882-1951. London, Macmillan and Co. , limited
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectcells, bookyear1920
