. Amphioxus and the ancestry of the vertebrates. Amphioxus; Sea squirts; Hemichordata. INTEKiXAL ANATOMY. 8i In the posterior chamber there are four pairs of much larger nephridia, which are similarly joined together by a prominent longitudinal duct from which short processes corresponding in number to the nephridia lead to the external apertures. The duct itself ends blindly at both ends, but is prolonged posteriorly far beyond the region of the nephridia (Fig. 40). The presence of this longitudinal duct in these worms is a very remark- able circumstance, but it is undoubtedly an expressi
. Amphioxus and the ancestry of the vertebrates. Amphioxus; Sea squirts; Hemichordata. INTEKiXAL ANATOMY. 8i In the posterior chamber there are four pairs of much larger nephridia, which are similarly joined together by a prominent longitudinal duct from which short processes corresponding in number to the nephridia lead to the external apertures. The duct itself ends blindly at both ends, but is prolonged posteriorly far beyond the region of the nephridia (Fig. 40). The presence of this longitudinal duct in these worms is a very remark- able circumstance, but it is undoubtedly an expression of the same phenomenon as the anastomoses between successive nephridia which have been described by EisiG for the Capitellidae, as well as the complicated series of anastomoses which convert the entire nephri- dial system into a marvel- lous network of tubules dis- covered by A. G. Bourne in the marine leech, Pon-. Fig. 40. — Schematic lateral view of anterior end of Lanice couchlk^a to show the nephridia. (After Eduard Meyfr from Hatschek's Lehrbi/ck's der ^it\^ The ventral side of the body is to the left of the fit^ure. d. Longitudinal ducts of the nephridia. Position of external openings, f. Nephridial funnel ( —coelomic opening of nephridium). m. Position of mouth; hounded bv two prominent lateral tobdella, and by BeDDARD lobes, and fringed by a great number of " feelers," which are cut short in the figure. m the curious earthworm, /. Branchial tentacles (three on each side PerichcEta. of the body). The present state of our knowledge does not admit of an attempt to specify the particular type of nephridial system from which that of the Annelids, on the one hand,. 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 Willey, Arthur, 1867-. New York, London, Macmillan
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