The evolution of man: a popular exposition of the principal points of human ontogeny and phylogenyFrom the German of Ernst Haeckel . Fig. 169.—Orif^inal or primordial egg-cleavage. The parent-cell, orcytula, which resulted from the fertilization of the egg-cell, first breaks up,by a continuous and regular process of dirisiou, into two cells (.4), then intofour (B), then into eight (C), and, lastly, into very numerous cleavage-cells (/)). the Morula (Fig. 165), the parent-cell breaks up, by repeateddivision, into numerous cells. We have already minutelyexamined this important process ofegg-clea
The evolution of man: a popular exposition of the principal points of human ontogeny and phylogenyFrom the German of Ernst Haeckel . Fig. 169.—Orif^inal or primordial egg-cleavage. The parent-cell, orcytula, which resulted from the fertilization of the egg-cell, first breaks up,by a continuous and regular process of dirisiou, into two cells (.4), then intofour (B), then into eight (C), and, lastly, into very numerous cleavage-cells (/)). the Morula (Fig. 165), the parent-cell breaks up, by repeateddivision, into numerous cells. We have already minutelyexamined this important process ofegg-cleavage, and have found that allthe various modes of the latter aremodifications of a single mode, thatof original or primordial cleavage.(Of Chap. VIIL, p. 188.) In the Ver-tebrate line this palingenetic form of ^^,.. ^K^, 11 X 1 Fig. 170.—Mulberry egg-cleavage has been accurately re- , ^^ ^ ^ gfrm, or 56 THE EVOLUTION OF MAN. tained to the present time only by the Araphioxus, whileall other Vertebrates have assumed a modified kenogeneticform of cleavage. (Cf. Table III, vol. i. p. 241.) The lattercertainly originated at a later period than the former, andthe egg-cleavage of the Amphioxus is, therefore, extremelyinteresting (vol. i. p. 442). In this the parent-cell firstparts into two similar cells, the two first cleavage-cells(Fig. 169, A). From these, by continuous division, arise4, 8, 16, 32, 64 cells, etc., etc. (Fig. 169). The final result ofthis primordial cleavage was, we found, the formation of aglobular mass of cells, which was entirely composed of homo-geneous, undifferentiated cells of the simplest character(Figs. 170, and 171, E). On account of the resemblancewhich this globular mass of cells bears to a mulberry orblackberry, we called it the mulberry-germ, or 7)iorula. This morula evidently at the present day shows usthe many-celled animal body in the same entirely simp
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