. Catalogue of the Chaetopoda in the British Museum (Natural History). Oligochaeta; Polychaeta. Gills of Arenicola 57 qI A. assimilis from. New Zealand, l)ut has not been found in those from other localities. The dorsal axes of each gill are almost invariably the largest and evidently the oldest, judging by the number of their branches; new axes are added to the gill ventrally (see PI. XIII, Fig. 43). Gills are not present in the genus Arenicola on the first six segments; out of some thousands of specimens the writer has seen. Fig. 29.—A. ecaiidata. The dorsal (small) and ventral (larpe) crotc
. Catalogue of the Chaetopoda in the British Museum (Natural History). Oligochaeta; Polychaeta. Gills of Arenicola 57 qI A. assimilis from. New Zealand, l)ut has not been found in those from other localities. The dorsal axes of each gill are almost invariably the largest and evidently the oldest, judging by the number of their branches; new axes are added to the gill ventrally (see PI. XIII, Fig. 43). Gills are not present in the genus Arenicola on the first six segments; out of some thousands of specimens the writer has seen. Fig. 29.—A. ecaiidata. The dorsal (small) and ventral (larpe) crotchets of the same neuropodium of a specimen 200 mm. long. Fig. .30. — A. bra iic/t ialis. Crotchet from a specimen 230 mm. long. only one in which a gill—a very small one—was present on the sixth segment.^ In A. marina, pudlla, asdmilis var. affinis, loveni, cristata and glacialis the first gill is normally on the seventh segment, in A. assimilis (typical form) on the eighth segment, in A. hrancMalis on the twelfth, and in A. ecaiidata on the sixteenth. In A. marina, jmsilla, loveni and assimilis (including the variety) there are thirteen pairs of gills ; in A. cristata and glacialis eleven pairs; in A. hranchialis ' One of Eanzani's specimens of ^1. clavatus {= marina) possessed a small gill on the sixth 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 Ashworth, James Hartley, 1874-1936; Ashworth, James Hartley. London, Printed by Order of the Trustees of the British Museum
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