Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 126 VERTEBRATA. like organs—the so-called vascular glands, spleen—are inserted into the course of the lymphatic vessels. Urinary organs or kidneys are generally present. They have the form of paired glands and lie beneath the vertebral column. The first rudiments of the kidneys appeal- in the form of organs resem- Lc TJ: 'Ilk FIG. 580.—Diagrammatic longitudinal section through aii ideal vertebrate embryo (after Balfour). </, After the completion of segmentation, b, Later stage in w
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 126 VERTEBRATA. like organs—the so-called vascular glands, spleen—are inserted into the course of the lymphatic vessels. Urinary organs or kidneys are generally present. They have the form of paired glands and lie beneath the vertebral column. The first rudiments of the kidneys appeal- in the form of organs resem- Lc TJ: 'Ilk FIG. 580.—Diagrammatic longitudinal section through aii ideal vertebrate embryo (after Balfour). </, After the completion of segmentation, b, Later stage in which the mesenteron is being formed at the hind end of the embryo (gastrula). c, Stage in which the neural canal is closed and communicates with the alimentary canal. EC, ectoderm ; Hut, entoderm; Ms, mesoderm; Fh, segmentation cavity; -DA, alimentary cavity; Nr, neuraljcanal; C/i, note-chord. bling the segmental organs of Annelids. Peritoneal invaginations (urinaiy tubules), which communicate with the body cavity by funnel- shaped openings, come into connection with the primitive kidney-duct (archinephric duct) which is the first part of the system to appear (compare vol. i., p. 76, fig. 71). The ducts of the kidneys—the ureters
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