. Senescence and rejuvenescence. Age; Reproduction. 326 SENESCENCE AND REJUVENESCENCE The diminished cell 5i of the two-cell stage produces a definite part of the ectoderm, and the cells 52, ^3, and 54 of following generations each have a definite fate. In other words, various portions of the soma or body are segregated before the so-called germ Mesoderm I and Stomodeum Primitive germ cells Mesoderm II Fig. 142.—Diagram of the cell lineage in the early cleavage of Ascaris megalo- cephala: the black circles represent cells before chromatin diminution and the primitive germ cells which d
. Senescence and rejuvenescence. Age; Reproduction. 326 SENESCENCE AND REJUVENESCENCE The diminished cell 5i of the two-cell stage produces a definite part of the ectoderm, and the cells 52, ^3, and 54 of following generations each have a definite fate. In other words, various portions of the soma or body are segregated before the so-called germ Mesoderm I and Stomodeum Primitive germ cells Mesoderm II Fig. 142.—Diagram of the cell lineage in the early cleavage of Ascaris megalo- cephala: the black circles represent cells before chromatin diminution and the primitive germ cells which do not undergo diminution; the unshaded circles with four black dots about them represent the cells which undergo diminution, and the unshaded circles alone, the cells after diminution. The further history of the various groups of cells is indicated by the words, "ectoderm," etc. After Boveri, 'lo. The undiminished cells show in all cases a slower rate of division than those in which diminution has occurred, and there is no evi- dence to show that the differences in the behavior of the chromatin are anything more than visible indications or expressions of differ- ences in rate of metabolic activity. It is quite possible that the undiminished cells become germ cells because they have a low. 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 Child, Charles Manning, 1869-1954. Chicago, Ill. , The University of Chicago Press
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectreproduction, bookyea
