Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 KEMEETOI. 341 Fig. 277.—Filidium (after E. Metschnikoff). a, free swimming larva vnih invaginated cavity ; b, later stage, helmet-shaped; E, E' the tvfO pairs of ectodermal invaginations; D, alimentary canal. cocoon. Some forms, as Prosorochmus Claparedli and Tetrastemma ohscurum, are viviparous. Some of the Anopla develop with a metamorphosis. The larva is ciliated and m ay pass through a free - swimming stage, in which case it is k
Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 KEMEETOI. 341 Fig. 277.—Filidium (after E. Metschnikoff). a, free swimming larva vnih invaginated cavity ; b, later stage, helmet-shaped; E, E' the tvfO pairs of ectodermal invaginations; D, alimentary canal. cocoon. Some forms, as Prosorochmus Claparedli and Tetrastemma ohscurum, are viviparous. Some of the Anopla develop with a metamorphosis. The larva is ciliated and m ay pass through a free - swimming stage, in which case it is known as the Fili- dium, or it may be without such a stage {Type ofDesor). In both cases the perfect worm is deve- loped within the skin of the ciliated larva. The Pilidium larva is helmet-shaped, and was formerly described as the species of a supposed independent genus, Pilidium, and presents many analogies to the Echinoderm larva. In the case of the Pilidium, the segmentation is regular, and results in the formation of a spherical ciliated em- bryo, which is hatched and becomes a free-swimming larva; the archenteron is then formed by invagina- tion ; and at the side of the embryo, opposite the blasto- pore, a long flagellum is developed (fig. 277, a). On each side of the mouth a broad lobe grows out, the edges of which are fringed with cilia (fig. 277, h). Two pairs of invaginations of the ectoderm now make their appear-
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