294 



Balanid.i?.- 



-ANNELIDA.- 



-Annei.ida. 



the whole world, the greater uumber however inhabit- 

 ing the warmer, temperate, and tropical seas. Tlie 

 name of barnacle shell was originally given to tlie 

 genus Lcpas, which may be known by the head or 

 capituhim being compressed and composed of five 

 approximate valves. They derive this name from its 

 being at one time believed that they gave origin to the 

 barnacle goose ! 



rA.Mii.Y ir.— BALANID^E {Sessile Clrrlpcth, or 

 Sca-acurns). 



The Balanida: are characterized by their being 

 fi,\cd to snbmarine bodies without the intervention of 

 a peduncle. The body of the animal is inclosed in a 

 cylindrical or bell-shaped tube open at the top, formed 

 of several valves united together, side by side, by a 

 dcntated suture, and covered by what is called an 

 operculinn, which consists generally of four valves 

 nearly equal-sized and sunk into a flexible skin, 

 allowing them a considerable degree of motion. The 

 base by which they are fixed is a shelly plate. The 

 species are numerous and most widely dilfnscd, taking 

 possession of rocks, ships, timber floating or at 

 rest, shells of Crustacea and Mollusca, &c. Some of 

 them are of considerable size, and one species of 

 the genus Balanus {D. ]isittaccu.i) found on the coast 

 of Chili, growing to the size of five or six inches, 

 forms a very common and liighly esteemed food for 

 the natives, who call it 2>lco. The llesh is said to equal 



in richness and delicacy that of the crab. Anotlicr 

 species, B. tudinnahulum (fig. 200), is equally prized by 



Biilaiuis Tintinnabuliim. 



the Chinese, the flesh of which is said to resemble the 

 lobster. Some of the species, as in Atasta, are found 

 attached to sponges, while others, as in P/p-goma, are 

 embedded in corals. The species of the genus Curomiln 

 and Tnhicinella, attach themselves to the bodies of 

 whales ; and as they increase in size their shells arc 

 proportionally enlarged by the addition of new matter 

 to the base of the valves, and they gradually raise 

 themselves out of the substance of the skin in whicli 

 they are ininiorscd. 



Class — ^ANNELIDA (Annelides, or Red Worms). 



Tun class Annelida, as now constituted, is composed 

 (if a series of animals which form only a small part of 

 tlie great heterogeneous class Vermes, or Worms, of 

 Linnffius. They are distinguished, however, from all 

 other worms by the fact that they possess red or 

 coloured blood, and hence are often called by the name 

 of Red Worms. This peculiarity was considered of 

 such importance by Cuvier that he placed them in his 

 last edition of the " Rcgne Animal" at the head of the 

 sub-kingdom Articulata. Their general appearance 

 nevertheless seems to point them out as the represen- 

 tatives of tlie larval rather than the perfect state of 

 insects, and thus to indicate their proper position to be 

 below both Insects and Crustacea. 



Annelides, then, are worms with red or coloured 

 lilood, circulating in a double system of complex vessels, 

 with a nervous system consisting of a double central 

 cord, and respiring by organs which are either developed 

 cxternallj' or are spread over the surface of the skin, or 

 concealed internallj'. The body, which is more or less 

 elongated, is always divided into numerous rings 

 {aniiull), from which circumstance the whole class 

 derives its name. The first of these rings contains the 

 mouth and the principal organs of sense. It is called 

 the head, but in outward appearance scarcely differs 



from the rest, which all agree in having the same form 

 and nearly the same size throughout. None of tlie 

 Annelides are possessed of true feet or articulated limbs, 

 but the greater number of them are provided with 

 hairs or hooks, or bundles, of bristles which supplj' their 

 place, while others have a suctorial disc which serves 

 them for progression. Their antenna (when they 

 possess them) are seldom jointed, and the organs of 

 their mouth consist of jaws, more or less powerful, or 

 of a simple tube. Tlie epidermis or external skin is 

 very thin, and is not ciliated except where it covers tlie 

 external branchire. The sense of touch is chiefly deve- 

 loped at the two first rings of the body, and exists cither 

 in form of a tentacular proboscis, contractile antenna"', 

 or processes of variable number and shape called cirrhi. 

 In a great many of the Annelides tlie eyes are wanting ; 

 in some they are represented by black dots merely, or 

 eye-specks, which in the leeches and some others are 

 numerous, and are considered to be light-perceiving 

 organs. The digestive canal is usually straight, rarely 

 having convolutions. 



The skin in many of the species secretes a quantity 

 of mucus which covers the body, and by means of whit:!] 

 some of them glue together pieces of shell, grains of 

 sand, &c., so as to form a tube to lodge themselves in. 



