. Darwin, and after Darwin. An exposition of the Darwinian theory and a discussion of post-Darwinian questions. Evolution; Heredity. 1^8 Darwin, and after Darwin, pushed inwards until they come into contact with those at the opposite pole of the ovum. Consequently, instead of a hollow sphere of cells, the ovum now becomes an open sac, the walls of which are composed. Fig x2 A, Gastrula of a Zoophyte KGastrophysema) (AftermckS B,GastrulaofaWorm^^a^V/a). (AfterKowalevskyO ^ Ga^rulaoian'Echinoderm iUraster). ^After A Ag^ssjz) D Gastrula of an Arthropod {^NaupHus. (After Hackel.) E


. Darwin, and after Darwin. An exposition of the Darwinian theory and a discussion of post-Darwinian questions. Evolution; Heredity. 1^8 Darwin, and after Darwin, pushed inwards until they come into contact with those at the opposite pole of the ovum. Consequently, instead of a hollow sphere of cells, the ovum now becomes an open sac, the walls of which are composed. Fig x2 A, Gastrula of a Zoophyte KGastrophysema) (AftermckS B,GastrulaofaWorm^^a^V/a). (AfterKowalevskyO ^ Ga^rulaoian'Echinoderm iUraster). ^After A Ag^ssjz) D Gastrula of an Arthropod {^NaupHus. (After Hackel.) E Ga^^™^ of a Mollusk {^Limn^us^. (After Rabl.) F-G-J^la of a Ve te a^e ^An^phioU. (After Kowalevsky.^ In all. d, mdtc^es tje "Ue t-1 cavity- 0 the primitive mouth; s, the cleavage-cavity, i, the enao derm, or intestinal layer ; e, the ectoderm or skm-layer. Of a double layer of cells (C). The ovum is now what has been called a gastrula; and it is of importance to observe that probably all the Metazoa pass through. 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 Romanes, George John, 1848-1894. Chicago The Open Court Pub. Co


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