. The elements of experimental embryology. Embryology, Experimental; Embryology. 96 CLEAVAGE AND DIFFERENTIATION eggs involves a decrease in the activities of the cytoplasm, or, in other words, a relative increase in the inertia of the mass of yolk. At all events, the splitting into two of the blastopore lip has been observed in such eggs, at the onset of gastrulation.^ An additional result obtained in these experiments is cases of disorganised growth, leading to tumour-like proliferations, which increase at the expense of the embryo itself, may give rise to metastases, and can be propagated b
. The elements of experimental embryology. Embryology, Experimental; Embryology. 96 CLEAVAGE AND DIFFERENTIATION eggs involves a decrease in the activities of the cytoplasm, or, in other words, a relative increase in the inertia of the mass of yolk. At all events, the splitting into two of the blastopore lip has been observed in such eggs, at the onset of gastrulation.^ An additional result obtained in these experiments is cases of disorganised growth, leading to tumour-like proliferations, which increase at the expense of the embryo itself, may give rise to metastases, and can be propagated by grafting (fig. 43).. Fig. 43 The effect of delayed fertilisation in frogs' eggs. Duplication, teratological monstrosities, and tumour-like growths in tadpoles derived from late-fertilised eggs (over 3 days over-ripe). Top left, anterior duplication, the upper head im- perfect, with single sucker. Top right, tadpole with irregular tail and rudimentary secondary ("parasite") head. Below, larva with much reduced head and tumorous growths ventrally. (Redrawn after Witschi, Verh. Naturfursch. Ges. Basel, XXXIV, 1922.) §3 Turning now to the experiments of isolating blastomeres in other groups of animals, it was found that the results differ considerably in the various groups. In some forms, the isolated blastomere de- velops into a complete and normally proportioned larva, differing from a normal larva merely in its small absolute size. In other forms, the isolated blastomere is incapable of doing this, and gives rise to a partial structure only. As extreme examples of these two types we may take the Hydrozoa and the Ascidians, respectively. ^ Witschi, 1922, 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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