216 SABELLIim 



segmental organs of the ordinary type with ventral nephridiopores. Neural canals largely 

 developed. Neither thoracic membrane nor operculum. 



Tube cylindrical, of mucine, leathery, or membranous, coated with dark mud, rarely 

 with sand or other material. 



The general structure of this and several of the succeeding genera has been given in 

 the ' Annals of Natural History ' lately, 1 so that it will only be briefly alluded to under the 

 species dealt with. 



The term " Sabella " was employed by Linnaeus in the tenth edition of the ' Systema 

 Naturae ' to designate a form similar to the Nereides with a tube of grains of sand, and 

 two thick tentacula behind the head. 



Cuvier noted that the members of the group rarely possessed a calcareous tube, whilst 

 they had the same fan-like gills as the Serpulae, and in many the same thoracic 

 membrane. 



The Sabellids were ranged under his comprehensive group " Annelides Serpulees " by 

 Savigny (1820) — along with Amphictenids, Arenicolids and other forms. The special 

 genus Sabella (Genus XXI) was, however, described with considerable minuteness and 

 care. He made three tribes, viz. (1) Sabellae Astartae, (2) S. Simplices and (3) S. Spiro- 

 graphes. 



The circulation of the Sabellids was stated by Milne Edwards 2 (1838) to be akin to 

 that of Nephthys and the Nereids. A dorsal and a ventral trunk are present, whilst the 

 inner aspect of the integument is supplied with a multitude of vascular filaments for the 

 secretory organs, and the bases of the feet present also a capillary rete which probably 

 aids in respiration, but the main respiratory organs are the cephalic fans in front. 



The elder Sars did much to place the genera of this group on a proper footing by 

 giving carefully revised characters. 



It is difficult to distinguish the Glymeneis stigmosa of H. Rathke, 3 in his " Fauna 

 Norwegens " (1843). It is apparently a Sabellid, and at first sight might pass for Chone 

 infundibuliformis without branchiae, but the author was familiar with that species, and 

 would not have omitted reference to the elongated anterior hooks. It is, at any rate, a 

 Sabellid. 



According to De Quatrefages (1850), the cephalic ganglia of Sabella flabellata form 

 two pairs connected by a large commissure. Branches from these go to the branchiae 

 and to the eyes. The oesophageal connectives are extremely short. The visceral system 

 seems to arise from the ganglia as a small twig on each side and furnished with two 

 ganglia. The ventral cords are separate throughout, though nearer each other posteriorly, 

 and the first ganglion is close to the cephalic ganglia, the others folio wing in each segment 

 and on each cord. Fine connecting trunks occur between each ganglion, whilst 

 branches from the latter pass to the muscles and other organs. He mentions that in 

 the branchiae of the Sabellidae and Serpulidae are venous and arterial twigs which mingle 

 in a system of vessels, the walls of which cannot be distinguished from the surrounding 

 tissues, and in which respiration is carried on through the thin covering tissues and 



1 ' Ann. Nat. Hist./ ser. 8, vol. xvii, 1916, p. 1. 



3 Op. cit., p. 212. 



3 < Nova Acta Cur./ Bd. xx, p. 228, Tab. ix ; figs. 10—14. 



