. The Biological bulletin. Biology; Zoology; Marine biology. 580 HENRY J. FRY manner, they are smaller. If these bodies are gradually destained, while watching the process, they do not lose their color while main- taining their characteristic size, but throughout the process they remain intensely black and become progressively smaller until they disappear. When such completely destained preparations are run up and studied in the usual way they show fibers which come to a point without the presence of a body. This is the case for example, in brain cells of Squalus embryos which have a centriole
. The Biological bulletin. Biology; Zoology; Marine biology. 580 HENRY J. FRY manner, they are smaller. If these bodies are gradually destained, while watching the process, they do not lose their color while main- taining their characteristic size, but throughout the process they remain intensely black and become progressively smaller until they disappear. When such completely destained preparations are run up and studied in the usual way they show fibers which come to a point without the presence of a body. This is the case for example, in brain cells of Squalus embryos which have a centriole-like mid-body (Fig. 11). The usual hypothesis that mid-bodies of animal cells are related in some way to the cell-plate of plant cells is not consistent with the behavior of mid-bodies as here described. The cell-plate is associated with a broad spindle which has distinct fibers in the mid-region (Fig. 13), whereas the mid-body is associated with a disintegrating spindle, and only after its fibers have been focalized. In most in-. FiGS. 13-15. Resemblances between the cell-plate of plant cells and mid-bodies of animal cells. Fig. 13: cell plate in pollen mother cells of Fritillaria (Strasburger, 1888). Fig. 14: fully formed mid-body in Romalea spermatogonia (Wilson, 1928). Fig. 15: early stage during formation of mid-body in epithelial cells of the salamander lung (Flemming, 1891). stances, regardless of their diversity in shape, mid-bodies are single structures which do not resemble cell-plates in any way. In certain cases, however, there is enough resemblance to have given rise to the hypothesis. The mid-body which is composed of a row of granules simulates the fixed cell-plate to some extent, but the differences are marked (Figs. 13 and 14). Also, there is occasionally a brief phase during the formation of a single mid-body when several granules are present (Fig. 15) that calls to mind the cell-plate. In general, however, it seems that the mid-body and the cell-plate have n
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