. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 362 C. D. DARLINGTON of it (Fig. 12). Repelling one another from their spindle attachments the pairs of chromatids associated at these points pass to opposite poles. Those pairs distal to the first chiasma therefore have to separate and the strain often draws them into a fine thread. Exceptionally a connection is seen between the separating chromatids (Fig. 13), as already noticed in Hyacinthus and Stenobothrns. This connection is as yet unexplained. Exceptionally also two of the shorter chromosomes are found to be un- paire
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 362 C. D. DARLINGTON of it (Fig. 12). Repelling one another from their spindle attachments the pairs of chromatids associated at these points pass to opposite poles. Those pairs distal to the first chiasma therefore have to separate and the strain often draws them into a fine thread. Exceptionally a connection is seen between the separating chromatids (Fig. 13), as already noticed in Hyacinthus and Stenobothrns. This connection is as yet unexplained. Exceptionally also two of the shorter chromosomes are found to be un- paired and may lag and divide at the first division. This failure corre- sponds with observations during prophase and, as will be seen, is related to conditions of chiasma formation. SHOKT. FIG. 16. Graph showing variation in chiasma frequency in the long, medium, and short types of chromosome. Second Division.—During the interphase and early metaphase of the second division the pairs of chromatids are held together only at their spindle attachments (Fig. 14). They suddenly come together, immedi- ately before anaphase, it must be presumed, for they are rarely seen together during metaphase and then only touching at the ends (Fig. 15). Syndiploidy.—Groups of from two to six spermatocyte nuclei are often found closely appressed, between pachytene and diakinesis; and at metaphase, in a corresponding proportion of cells, fusion of the adjoining plates of chromosomes is seen. Where only two nuclei lie together the result is a regular fused spindle but, with a larger number, the chromosomes no longer orientate themselves regularly. These re-. 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 Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-195
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
