. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 52 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. place in a right spiral, whereas that of the third presented the character of a left spiral. Applying the system of nomenclature which I have adopted to the derivatives of the third generation,, we fiud that cells of the lower quartet will be designated by the exponent , and the upper by It will be convenient in the further discussion of quartets to refer to them simply by their exponents, without reference to the indi- vidual cells of which they are compose
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 52 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. place in a right spiral, whereas that of the third presented the character of a left spiral. Applying the system of nomenclature which I have adopted to the derivatives of the third generation,, we fiud that cells of the lower quartet will be designated by the exponent , and the upper by It will be convenient in the further discussion of quartets to refer to them simply by their exponents, without reference to the indi- vidual cells of which they are composed. It will be seen from Figures 17 and 19 (Plate II.) that the dorsal and ventral cross furrows at the close of this stage do not lie at right angles to each other, as they did at the end of the four-cell stage, but that they cross each other at an angle as much less than 90° as is represented by the shifting of the cells to produce the spiral, i. e. they now cross at about 45°, as seen in the accompanying diagrams (Figures A and B). Figure A. Figure 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 Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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