ANNELIDES: SERPULAD^E. 467 



SUB-SECTION I. 

 THE ORDER OF ANNELIDES. 



THIS Order comprises worms which have red blood 

 that circulates in a double system of complicated vessels. 



SERPULAD.E, OR SERPULA FAMILY. This Family em- 

 braces marine worms whose organs of respiration are 

 in tufts attached to the head and anterior part of the 

 body. In most cases they live in tubes, and hence are 

 often called Tubicolae. In some the tubes are calcareous, 

 in others horny, the result of transudation ; others still 

 are formed of grains of sand, or other particles bound to- 

 gether by a membrane also transuded. 



The Genus Serpula has the anterior 

 portion spread out in the form of a disk 

 armed on each side with bundles of coarse 

 hairs, and on each side of the mouth is 

 a tuft of branchiae shaped like a fan, 

 and generally tinged with bright colors. 

 At the base of each tuft is a fleshy fila- 

 ment, one of which is always elongated, 

 and expanded at its extremity into a disk 

 which serves as an operculum, and seals 

 up the opening to the tube when the 

 animal is withdrawn into it. The cal- Marine 

 careous tubes of the serpulae cover submarine bodies. 



ARENICOLAD^E, OR SAND-WORM FAMILY. This Fam- 

 ily comprises worms which have the organs of respiration 

 in the form of trees, tufts, laminae, or tubercles, placed on 

 the middle of the body. They are marine, and known as 

 Dorsibranchiatae, and live free in sand, mud, or water. 



LUMBRICID.E, OR EARTH-WORM FAMILY. This Fam- 

 ily embraces worms which have no visible external organs 

 of respiration, but appear to respire by the entire surface. 



The Genus Ltimbricus contains the common Earth- 



