. Chimæroid fishes and their development. Fishes; Chimaeridae. ^1 fs^^'f. Fig. 63.—Sagittal section of earliest gastruia. n, Archenteric cavity. />/•, Blastopore. i(, Segmentation cavity. 1-V indicate position of nuclei in yolk region. Figs. 63 A and B.—Details of foregoing section at anteriormost and posteriormost margins respectively. germinal wall, finally, cellular additions to the blastoderm are being made. Note- worthy in the present section are the vacuoles which pass deeply into the yolk and suggest, as we have already noted, modified or suppressed lines of cleavage; espe- cially we
. Chimæroid fishes and their development. Fishes; Chimaeridae. ^1 fs^^'f. Fig. 63.—Sagittal section of earliest gastruia. n, Archenteric cavity. />/•, Blastopore. i(, Segmentation cavity. 1-V indicate position of nuclei in yolk region. Figs. 63 A and B.—Details of foregoing section at anteriormost and posteriormost margins respectively. germinal wall, finally, cellular additions to the blastoderm are being made. Note- worthy in the present section are the vacuoles which pass deeply into the yolk and suggest, as we have already noted, modified or suppressed lines of cleavage; espe- cially well marked are those occurring in the fine 3'olk on either side of the blasto- derm, since they form a series of vertical fissures and mark off masses of fine 3'olk containing nuclei. The vacuoles also occur throughout the neighboring coarse yolk, and in connection with their appearance there we note the presence of merocytes which have traveled, as at iv, iii, 11 or i, far out over the yolk. We note, lastly, the way in which the fine yolk passes down in rifts into the coarse yolk, for this suggests again the modified holoblastic condition of the egg. The next stages in gastrulation deal with the extension of the blastoderm over the yolk. Thus in fig. 64 is given a sagittal section of a stage in which the diameter. 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 Dean, Bashford, 1867-1928. Washington, D. C. , Carnegie Institution of Washington
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectfishes, bookyear1906
