. Text-book of embryology. Embryology. 122 INVERTEBEATA CHAP. Eunning round the edge of the larva under the prototroch a nerve- rmg has been detected. The development of the Pilidium is now complete, and it swims about at the surface of the sea feeding on microscopic organisms which are whisked into its mouth by the action of its cilia. After. Fia. 97.—^A Pilidmm larva shortly before its metamorphosis. (After Metschnikoff.) Letters as before. In additioD, , anterior iniaginal disc; , rudiment of cephalic slit; pr, rudiment of ; , posterior imaginal disc ; oes, oesophagus
. Text-book of embryology. Embryology. 122 INVERTEBEATA CHAP. Eunning round the edge of the larva under the prototroch a nerve- rmg has been detected. The development of the Pilidium is now complete, and it swims about at the surface of the sea feeding on microscopic organisms which are whisked into its mouth by the action of its cilia. After. Fia. 97.—^A Pilidmm larva shortly before its metamorphosis. (After Metschnikoff.) Letters as before. In additioD, , anterior iniaginal disc; , rudiment of cephalic slit; pr, rudiment of ; , posterior imaginal disc ; oes, oesophagus. about two weeks it begins its metamorphosis. This has been described by Metschnikoff (1869) and Salensky (1886). On the flattened under side four ciliated invaginations of the ectoderm are formed. These are termed the amniotic invaginations, and their deeper portions are the imaginal discs. Two of these invaginations are situated opposite one another on the right and left sides of the animal respectively, in front of the mouth, and two others are similarly situated behind the mouth. Each of them grows and deepens, extending upwards over the surface of the globular. 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 MacBride, E. W. (Ernest William), 1866-1940; Kerr, John Graham, 1869-; Heape, Walter, 1855-1929. London : Macmillan
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Keywords: ., bookcentury1900, bookdecade1910, bookpubli, booksubjectembryology
