. The elements of experimental embryology. Embryology, Experimental; Embryology. a Fig. 29 Cleavage asymmetry in Molluscs. The position of the large mesoderm cell (^d) is reversed in laeotropic and dexiotropic cleavage. (From Morgan, Experimental Embryology, Columbia University Press, igzj.) tubicolous Annelid worms, involves special problems of relative growth-rate, which are discussed by Przibram (1931 a). The most marked asymmetry known is that of Gastropod Mol- lusca, most of which manifest a marked torsion of the internal anatomy together with unequal development of many paired organs. In
. The elements of experimental embryology. Embryology, Experimental; Embryology. a Fig. 29 Cleavage asymmetry in Molluscs. The position of the large mesoderm cell (^d) is reversed in laeotropic and dexiotropic cleavage. (From Morgan, Experimental Embryology, Columbia University Press, igzj.) tubicolous Annelid worms, involves special problems of relative growth-rate, which are discussed by Przibram (1931 a). The most marked asymmetry known is that of Gastropod Mol- lusca, most of which manifest a marked torsion of the internal anatomy together with unequal development of many paired organs. In addition, a large number of forms have their shells twisted into a spiral, which is usually dextral. Here it has been shown that the dextral or sinistral type of structure is under the control of Men- delian factors, whose action, however, is delayed for a generation^ (see Chap. xii). The asymmetry of the a^dult is determined not by its own genetic constitution, but by that of the oocyte from which it arose, before it underwent the reduction divisions. The cleavage ^ Boycott, Diver, Garstang, and Turner, 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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