. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. FIG. 277.—Pilidium (after E. Metschnikoff). a, free swimming larva with invaginated cavity ; b, later stage, helmet-shaped ; E, E1 the two pairs of ectodermal invaginations; Z>, alimentary canal. R Am D. 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
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. FIG. 277.—Pilidium (after E. Metschnikoff). a, free swimming larva with invaginated cavity ; b, later stage, helmet-shaped ; E, E1 the two pairs of ectodermal invaginations; Z>, alimentary canal. R Am D. 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 imagina- tion ; and at the side of the embryo, opposite the blasto- poi'e, a long flagellum is developed (fig. 277, «). On each side of the mouth a broad lobe grows out, the ed^es of which are fringed o with cilia (fig. 277, b). Two pairs of invaginations of the ectoderm now make their appear- Oe FIG. 278.—Later stage of Pilidium, with tuft of cilia and enclosed Nemertine (after Biitschli); Oe, oesophagus; D, alimentary canal ; Am, amnion; -R, rudimentary proboscis of the Nemertine; So, lateral 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 Claus, Carl, 1835-1899; Sedgwick, Adam, 1854-1913; Sinclair, F. G. (Frederick Granville), b. 1858. London, Swan Sonnenschein & co.
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Keywords: ., book, bookcentury1800, bookcollectionbiodiversity, bookdecade1890
