LUMBBICUS. 133 



features, accompanied by delineations. It is probable that some of them 

 may be withdrawn, on farther examination, for the purpose of being 

 placed in more suitable positions. 



Segments, and hairs or bristles, are assumed as the most prominent 

 features commonly distinguishing individuals of the genus. 



In some, however, neither of these characters predominate over 

 others, their presence being somewhat equivocal. Nor shall I rigidly re- 

 ject what most naturalists have to accept as species. 



1. LUMBRICUS CIRRATTTS The Medusa Worm. CIRRATULUS BOREALJS, 

 Lamarck.* Plate XVIII. Figs. 1, 2, 3, 4. 



Length four inches, greatest thickness three sixteenths of an inch ; 

 body composed of numero us segments, and tapering towards each extremity. 

 Numerous long and flexible cirri invest the whole body, apparently some- 

 what cartilaginous, and consisting of an infinite number of rings. These 

 cirri originate from every second segment, no one being free of them. 

 Two rows run down the back, and continue nearly to the posterior ex- 

 tremity. All are longest towards the anterior extremity, shortening as 

 they descend. Many are necessarily omitted in the figure, Plate XVIII. 

 fig. 1, which would be otherwise confused and indistinct. A section of 

 one is represented as enlarged, fig. 2. A pencil of bristles, very difficult 

 to be observed, is placed on each side of each segment, sometimes appear- 

 ing as if only two of unequal length. But the incessant motion of the 

 animal, and their position, rendered the part of difficult determination by 

 the microscope. When the animal crawls, the cirri lie above each other 

 along the back, presenting a very singular aspect. The mouth is in the 

 anterior extremity, and the sustenance of the animal is probably derived 

 from mud. 



* Lamarck places this animal among the Annelides, but he thinks it does not belong 

 to the genus Lumbricus. Other authorities endeavour to constitute a different place for its 

 reception. The work of Andouin and M. Edwards. L'Histoire Naturette du Littoral de 

 la France, torn. ii. p. 271, PI. VII. may be profitably consulted. 



