. Comparative anatomy and physiology. Chap. III.] BRA CHIOPODA : BR } rozoA. 101 unequal valves which make up their shell, and by the characters of their nervous system. The so-called arms (Fig. 49 ; 6) are outgrowths of the prse-oral disc of the larva, at the edges of which the tentacles or cirri are set. This great development of their arms is to be correlated with the fixed habit of the Fig. 50.—Bugula purpurotincta. Nat. size. (After Hiucks.) Terebratula and Lingula (which is stalked) are ex- amples of this isolated and geologically ancient group. 2. The Bryozoa have likewise been
. Comparative anatomy and physiology. Chap. III.] BRA CHIOPODA : BR } rozoA. 101 unequal valves which make up their shell, and by the characters of their nervous system. The so-called arms (Fig. 49 ; 6) are outgrowths of the prse-oral disc of the larva, at the edges of which the tentacles or cirri are set. This great development of their arms is to be correlated with the fixed habit of the Fig. 50.—Bugula purpurotincta. Nat. size. (After Hiucks.) Terebratula and Lingula (which is stalked) are ex- amples of this isolated and geologically ancient group. 2. The Bryozoa have likewise been placed with the Mollusca; they are clearly degenerate forms which, by the characters of their larvse, appear to have been descended from an ancestor common to them and the Chaetopoda. Balfour has suggested that they become fixed by their prse-oral lobe. They live in colonies, and are the forms that are popularly known as sea-mats or sea-mosses (Fig. 50). 3. The Chsetognatlia (as represented by Sagitta) are forms that have relations to the Chastopoda and. 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 Bell, F. J. (Francis Jeffrey), 1855-1924. London, Cassell
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