66 INTRODUCTION TO ZOOLOGY. 



They present considerable diversity in size. In one tribe 

 (Nemertind) there are individuals not more than one or two 

 inches long, while others, of the same fraternity, attain the 

 enormous length of fifteen feet,* or, when artificially dis- 

 tended, of more than twenty yards. | The sea long-worm, for 

 so this species is named (Nemertes Borlasii), contracts in 

 spirits to one or *wo feet in length, and the thickness of an 

 ordinary quill. One was taken by Captain Fayrer, " holding 

 on to a bait on his long line, when he was fishing for cod off 

 Portpatrick."J 



In contrast with the freebooter, thus made prisoner while 

 on a predatory excursion, we may mention a species which is 

 so much broader and thicker than other Annelids as to have 

 lost its worm-like aspect. It is common around our coast, and 

 is popularly known as the sea-mouse (Aphrodita aculeata). 

 Besides being furnished with numerous fasciculi, or bunches of 

 stiff, sharp-pointed bristles, employed both as organs of motion 

 and weapons for defence, it is decorated with numerous soft, 

 silky hairs, of the most brilliant metallic colours, and highly 

 iridescent. Strange it may seem to us, that a worm, living 

 in the midst of the slime at the bottom of the sea, should 

 have a vesture which rivals, in the splendour of its hues, the 

 wing of the butterfly, or the plumage of the humming-bird I 

 But the beauty impressed on even the humblest of created 

 beings seems boundless as the beneficence of Him who called 

 them into being. 



We have enumerated four tribes of Annellata: 



I. The Suctorial, comprising the Leeches; 

 II. The Terricolous, including the Earth- worms ; 



III. The Tubicolous, which inhabit tubes ; 



IV. The Errantes, ' which are the most highly organized, 

 and the most locomotive. 



In respect to some worms, there are traditionary errors 



* Dr. Johnston in Mag. of Zoology and Botany, 1837, page 536. 



f This we state on the authority of Mr. R. Ball, who took one at 

 Clifden, Co. Gal way, which he ingeniously caused to distend itself, and 

 was thus enabled to ascertain its measurement. 



W. Thompson in Mag. Nat. Hist. vol. ii. JSTo. 13. 



Their respiratory organs are placed upon the back ; hence the term 

 applied to them bj r Cuvicr, Dorsibranchiate, from Dursum, the back ; 

 and bronchia, gills. 



