. The elements of experimental embryology. Embryology, Experimental; Embryology. 402 THE HEREDITARY FACTORS AND DIFFERENTIATION Another example is provided by the exposure of the eggs of the frog or of certain fish to the action of weak toxic substances. In such cases (already noted in Chap, ix, p. 348) the animals develop with one median cyclopic eye instead of the normal pair.^ Since it. Fig. 194 Absence of cohesion in the blastomeres of sea-urchin eggs in calcium-free sea- water, a-c, Successive stages in one egg. «, 2-cell stage. &, 4-cell stage, c, i6-cell stage. The cell-membrane has
. The elements of experimental embryology. Embryology, Experimental; Embryology. 402 THE HEREDITARY FACTORS AND DIFFERENTIATION Another example is provided by the exposure of the eggs of the frog or of certain fish to the action of weak toxic substances. In such cases (already noted in Chap, ix, p. 348) the animals develop with one median cyclopic eye instead of the normal pair.^ Since it. Fig. 194 Absence of cohesion in the blastomeres of sea-urchin eggs in calcium-free sea- water, a-c, Successive stages in one egg. «, 2-cell stage. &, 4-cell stage, c, i6-cell stage. The cell-membrane has become radially striated, and the cells fail to remain united, d. Disintegration of a blastula into its component cells when placed in the same medium. (After Herbst, from Jenkinson, Experimental Embryology, Oxford, 1909.) it known from palaeontological evidence that fish have possessed paired eyes since the Silurian dpoch, these experimental results are an illuminating example of the fact that hereditary factors, however long the time during which they have been transmitted to successive generations, can only produce their normal effects by interacting ^ Stockard, 1910; Bellamy, 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 Huxley, Julian, 1887-1975; De Beer, Gavin, Sir, 1899-1972. New York [Hafner Pub. Co. ]
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