. The cell in development and inheritance. Cells. Fig. 173. — Partial or meroblastic cleavage in the squid Loligo. [V^'^atase.] plicable to the inequalities of the first two divisions in annelids and gasteropods. It is conspicuously inadequate in the history of indi- vidual blastomeres, where the history of division has been accurately determined. In Nereis, for example, a large cell known as the first somatoblast, formed at the fourth cleavage (A", Fig. 171, E\ under- goes an invariable order of division, three unequal divisions being fol- lowed by an equal one, then by three other unequ
. The cell in development and inheritance. Cells. Fig. 173. — Partial or meroblastic cleavage in the squid Loligo. [V^'^atase.] plicable to the inequalities of the first two divisions in annelids and gasteropods. It is conspicuously inadequate in the history of indi- vidual blastomeres, where the history of division has been accurately determined. In Nereis, for example, a large cell known as the first somatoblast, formed at the fourth cleavage (A", Fig. 171, E\ under- goes an invariable order of division, three unequal divisions being fol- lowed by an equal one, then by three other unequal divisions, and again by an equal. This cell contains little or no deutoplasm and undergoes no perceptible changes of substance. The collapse of the rule is most complete in case of the rudi- mentary cells referred to above. In some of the annelids, in Aricia, where they were first observed,^ these cells are derived from the very large primary mesoblast-cell, which first divides into equal halves. Each of these then buds forth a cell so small as to be no larger than a polar body, and then immediately proceeds to give rise 1 Cf. Wilson, '92, ' 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 Macmillan
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectcells, bookyear1906
