. The cell in development and inheritance. Cells. Fig. 186. — Modification of cleavage in sea-urchin eggs by pressure. A. Normal eight-cell stage of Toxopneustes. B. Eight-cell stage of Echinus segmenting under pressure. Both forms produce normal Plutei. blastomeres in its pale non-granular character and in the presence of large oil-drops. If unsegmented eggs be subjected to pressure, as in Driesch's echinoderm experiments, they segment in a flat plate, all of the cleavages being vertical. In this way are formed eight-celled plates in which all of the cells contain oil-drops (Fig. 187, D\ If t
. The cell in development and inheritance. Cells. Fig. 186. — Modification of cleavage in sea-urchin eggs by pressure. A. Normal eight-cell stage of Toxopneustes. B. Eight-cell stage of Echinus segmenting under pressure. Both forms produce normal Plutei. blastomeres in its pale non-granular character and in the presence of large oil-drops. If unsegmented eggs be subjected to pressure, as in Driesch's echinoderm experiments, they segment in a flat plate, all of the cleavages being vertical. In this way are formed eight-celled plates in which all of the cells contain oil-drops (Fig. 187, D\ If they are now released from the pressure, each of the cells divides in a plane approximately horizontal, a smaller granular micromere being formed above, leaving below a larger clear macromere in which the oil-drops remain. The sixteen-cell stage, therefore, consists of eight deutoplasm-laden macromeres and eight protoplasmic micromeres (instead of four macromeres and twelve micromeres, as in the usual development). These embryos developed into free-swimming trocho- phores containing eight instead of foiir macromeres, which have the typical clear protoplasm containing oil-drops. In this case there can. 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
Size: 1602px × 1559px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectcells, bookyear1911
