TEBEBELLIDJE. 97 



In Terebella conckilega, Be Quatrefages 1 (1844) found the cephalic ganglia elongated 

 fusiform, with connectives in the middle line, and giving off three or four pairs of 

 nerves to the cirri. The oesophageal connectives are short and thick, and from their 

 anterior part a small branch with a ganglion may represent the visceral system. The 

 ventral chain is single in front (anterior region) with the usual ganglia. In the posterior 

 region the chain is double, though the ganglia are united by commissures as in Aonia 

 and Malacoceros. 



Johnston 2 (1845) constituted the family Terebellidas, which he separated from the 

 Pectinarians and Sabellarians. 



G-rube (1851) placed the Terebellidas between the Maldanidse and the Hermellidse, 

 a position less convenient than subsequent investigations proved, and like some of 

 his predecessors he included the Amphictenida3 and Ampharetidaa under the same 

 head — Terebelliformia — distinguishing them by the presence of paleae in the mouth- 

 segment. 



M. Sars did much to extend our knowledge of the northern species of Terebellids 

 in his various papers, adding such interesting forms as Terebellides, Amoea ; and in 1868 

 found the following forms at a depth of 300 fathoms, viz., Terebella artifex, Terebellides 

 stroemi, and Ereutho smitti? 



Dr. Thos. Williams (1858) examined the segmental organs in the thoracic region 

 of T. nebulosa and other species, one half being highly vascular, the other membranous 

 and excretory, the former being connected with the ovary or spermary, the latter being 

 the efferent channel. He held that the long glandular mass in front was a secretory 

 organ in connection with tube-formation. This family and the Arenicolidas were, he 

 stated, the only two in which the reproductive elements were shed into the body-cavity — 

 a statement which cannot now be made. He further observes 4 that " in the Terebellse 

 and Serpulas, which are cephalo-branchiate, the anterior extremity of the great dorsal 

 trunk enlarges fusiformly and propels the blood directly into the branchial appendages. 

 In these genera therefore this vessel becomes the branchial heart ; and the great ventral 

 trunk, into which the efferent branchial vessels empty themselves, becomes the systemic 

 aorta." 



Malmgren (1865) grouped the Terebellacea under five sub-families, viz., Amphi- 

 tritea, Polycirridea, Artacamacea, Trichobranchidea, and Canephoridea, and he gave 

 a useful syllabus of the genera under each. The Amphitritea presented a truncated 

 cephalic lobe with numerous canaliculated tentacles arising from a muscular lip, and 

 behind them numerous ocular points. Blood-vessels conspicuous. Branchiae generally 

 present. Bristles capillary and winged, generally in the anterior region of the body, 

 sometimes throughout the entire length. Avicular or rarely pectiniform hooks on tori, 

 and of similar structure throughout. This author has the credit of placing the structure 

 and arrangement of the bristles and hooks of the group on a proper footing. His 

 classification is as follows : 



1 Ann. Sc. nat./ 3 e ser., t. xiv, pp. 368—9. 



2 c Ann. Nat. Hist./ vol* xvi, p. 447. 



3 ' Yidensk.-Selsk. Forhandl./ 1868 (sep. copy), p. 10. 

 4f Rept. Brit. Assoc./ 1851. 



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