APPENDIX. 333 



extremity of the body, while the front portion projects freely and 

 floats about in the water. But Bonnet asserts the contrary : " Au 

 reste, c'est la partie posterieure du ver qui sort hors du tuyau, et 

 qui s'agite continuellement en divers sens : I'anterieure demeure tou- 

 jours cachee dans la boue." — Bonnet, InsectoL ii. 182. 



Miiller says that his Lumbricus tubifex is " bifariam aculeatus ; " 

 but the description in other respects agrees so well with our worm, 

 that I have not hesitated about the name. 



Saenuris vagans (page 65). 



I find this minute worm in abundance in the soil under the moss 

 on rocks over which water trickles. It creeps quickly enough in the 

 soil, but makes slow progress in pure water, where it wriggles and 

 bends itself into a simple curve. From the simplicity of its structure 

 it might be referred to the Naides, but the bristles are curved. 



Head obtusely pointed ; mouth inferior, between it and the second 

 segment, without a proboscis. Body filiform, smooth and even, 

 equal at both extremities, consisting of about fifty equal segments 

 divided by a simple line ; anal segment obtusely pointed. Intestine 

 regularly segmented, without any lateral caeca : no distinctly separated 

 stomach. Segments armed with spinets only, in four series, fascicu- 

 late, with from three to eight spinets in each fascicle, fan-shaped : 

 there are a greater number of spinets in the ventral series than in the 

 dorsal, even on the same segment. The spinets are colourless, 

 slightly bent, acute at the outer extremity, much shorter than the 

 diameter of the segment. 



Saenuris variegata (page 65). 



Body from an inch to 2 inches long, slender, filiform, narrowed a 

 little at each end, chiefly so at the anterior, smooth, annulose, of a 

 reddish -brown maculated colour, with a vessel of a fine ruby-red 

 colour running down the middle ; the sides straw-yellow and finely 

 crenulate. Anterior end acute, pale ; and the posterior extremity is 

 often also colourless. The bristles are very short and retractile ; they 

 are in four series, and there are about four bristles in every fascicle. 



The natural or ground colour of the body seems to be a straw- 

 yellow ; and the red is variable in extent, and in the character of the 

 markings. The intestine is divided, like a vertebral column, by a 

 series of strictures corresponding to the rings ; and from these stric- 

 tures there is sent oif, to each side, several filiform caeca, which form 

 a series of quadrangular brown spots arranged along each side of the 

 central aspect — "utrinque maculis quadratis pinnata*." These 

 spots are often very obvious, but only in individuals which seem to 

 have wanted food for some time ; and more commonly the spots are 



* " This worm is remarkable by its vascular system. The dorsal vessel in it, 

 at each segment, gives oif a branch at right angles, which terminates in a digitate 

 manner in csecal twigs, as in fact Treviranus had already noticed." — Re^. on ZooL, 

 Ray Soc. 1847, p. 510. 



