. The cell in development and inheritance. Cells; Cells. 314 THEORIES OF INHERITANCE AND DEVELOPMENT to the whole must not, however, be conceived as a merely geometri- cal or mechanical one ; for, in different species of eggs, blastomeres may exactly correspond in origin and relative position, yet have entirely different morphological value. This is strikingly shown by. Fig. 138. — Partial larvae of the ctenophore Beroe. [Driesch and Morgan.] A. Half i6-cell stage, from an isolated blastomere. B. Resulting larva, with four rows of swim- ming plates and three gastric pouches. C. One-fourth i6-c
. The cell in development and inheritance. Cells; Cells. 314 THEORIES OF INHERITANCE AND DEVELOPMENT to the whole must not, however, be conceived as a merely geometri- cal or mechanical one ; for, in different species of eggs, blastomeres may exactly correspond in origin and relative position, yet have entirely different morphological value. This is strikingly shown by. Fig. 138. — Partial larvae of the ctenophore Beroe. [Driesch and Morgan.] A. Half i6-cell stage, from an isolated blastomere. B. Resulting larva, with four rows of swim- ming plates and three gastric pouches. C. One-fourth i6-cell stage, from an isolated blastomere. D. Resulting larva with two rows of plates and two gastric pouches. E. Defective larva, with six rows of plates and three gastric pouches, from a nucleated fragment of an unsegmented egg. F. Similar larva with five rows of plates, from above. a comparison of the polyclade egg with that of the annelid or gasteropod (Fig. 137). In both cases three quartets of micromeres are successively budded off from the four cells of the four-cell stage in exactly the same manner. The iirst quartet in both gives rise to ectoderm. Beyond this point, however, the agreement ceases;. 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 Macmillan company
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectcells, bookyear1896
