TUB! COL.!;. 



391 



siders them as the Intermediate hnk hetwecn the Vertebr;ita and Annulo?a, ob- 

 serving upon the curious circurn- 



Stance that these two subkingdoms, 

 so highly organized in the scale of 

 the creation, should be linked to- 

 gether by a group exhibiting such 

 great imperfections of structure. 

 r>fi|,aid.^-.- .Liia.:h.-.i ti,.-r,.[.,. ^ Ihis class has been greatly neg- 



lected in this country. Dr. Johnston has, however, described various species (especially 

 in the Annals of Natural History, for February, 1840), and Mr. Mac Leay, in the same 

 number,"^ has noticed several fossil species. It is. however, in France that the greatest 

 attention has been paid to them, especially by Savigny, Audouin, and Milne Edwards.] 



THE FIRST ORDER OF ANNELIDES. 



THE TUBICOL.E. 

 Some species of this division form a homogeneous, calcareous tube, which probably results 

 from their transudation, like the shells of the Mollusks, but to which the muscles do not adhere ; 

 others construct tubes, by agglutinating grains of sand, fragments of shells, and particles of 

 mud, which they join by means of a membrane, which likewise is doubtless transuded; lastly, 

 there are some, the tubes of which are entirely membranous, or horny. 



To the first group Ijcloug 



Serfula, Linn., — 

 Tlie calcareous tubes of which invest, from their twisting aliout, fragments of stones, shells, and all sorts of 

 submarine matters. The truncation of these tabes is either round or angular, according to the species. 

 The animal within has its hody composed of a great number of segments ; its fore-part widened 

 into a disk, fui-uished on each side ^vith many hundles of stiff hri^tles ; and on either side of its 

 mouth is a tuft of fan-like gills, in general vividly coloured. At the base of each tuft is a 

 fleshy filament ; and one of the^e, on the right or left side indifferently, is always prolonged and di- 

 lated at its extremity mto a variously-formed disk, which serves for an operculum and mouth at the 

 entrance of the tuhe when the creature retires into it. 



The common sjiecies {S. coniortuplicata, Ellis), has a round and twisted tube three 

 lines in diameter. Its operculum is funnel-shaped, and its ^ills often of a fine red, or 

 varied with yellow, violet, &c. This animal quiL-kly fahricates its tube of mud, a^^Muti- 

 natiiig into it whatever small objects he around. 



There is another and smaller species on our coasts, with a club-shaped operculum, 

 armed with two or three little points {S. venniculnris, Gmeliu). Its g-ills are sometimes 

 blue. Notliing is more beautiful to see than a ;;roup of these Sej-pula? when their wino^s 

 are expanded. 



Ill other species, t!ie operculum is flat, and bristled with more numerous points. 

 These are the (jolcolaria, Lamarck. 



There is one in the Antilles (-S'. g'uianica, Pallas), which is found among; the Madre- 

 pores, and tlie tube of which is often inclosed in their mass. Its ffills roll up spirally 

 when they are withdrawn, and the operculum is firmed with two little branching; horns 



r b(.J)- 



Fn'. 



