CIRCULATION IN THE ANNELIDA. 



235 



dilatations, about twelve in number, resembling a 

 string of beads.* 



In the Lumbricus terrestris, or common earth- 

 worm, there are only five pair of these vessels : 

 they have been described and figured by Sir E. 

 Home ;t but the most full and accurate account of 

 their structure has been given by Morren, in his 

 splendid work on the anatomy of that animal.j; 

 Fig. 349, which is reduced from his plates, repre- 



349 



sents these singular appendages to the vascular 

 system of the earth-worm, separated from their 

 attachments, and viewed in connexion only with 

 the dorsal and abdominal trunks in which they ter- 

 minate. The abdominal vessel (a, a), on arriving 

 near the oesophagus, is dilated, at the point b, into 

 a globular bulb (c), which is followed, at equal 

 intervals, by four others (c, c). From each of these 

 bulbs, or ventricles, as they are termed by Morren, 

 a vessel (d) is sent off" at right angles, on each 

 side ; this vessel also enlarges into several nearly 



* They are termed by Duges, Vaisseaux moniliformes, ou dorso- 

 abdominaux. — Annales des Sciences Naturelles, xv, 299. 



t Philos. Transact, for 1817, p. 3 : and PI. iii. Fig. 4. 



I " De Lumbrici terrestris Historia naturalis, necnon Anatomiu 

 Tractatus." Qto. Biuxelles, 1829. 



