VERMES. 83 



retractile spine. If a third animal exhibits neither of those features, it 

 must be placed in a separate group. Therefore I shall avail myself of 

 that distinction. 



It would require time, accidental observation, and opportunity, to 

 determine whether all varieties of the vermicular tribes under considera- 

 tion do not involve their long, slender, unmanageable bodies, if truly such, 

 in a knot. 



a. GORDIUS FUSCUS. The Brown Gordius. Plate XII. 



Length eighteen inches ; breadth an eighth of an inch ; body flat- 

 tened ; extremities obtuse, anterior generally somewhat angular. Back 

 mottled brown, belly pale. Motion smooth and gliding. 



This animal involves itself in a knot. Here there is no sensible cleft 

 or groove of the anterior, nor any spinous prolongation of the posterior 

 extremity. 



The mouth is apparently in the anterior part. In pale specimens, 

 specks are perceptible on the margin. Being extremely minute, they 

 will be sought in vain on those that are dark. Head of a specimen shew- 

 ing the specks. Plate IX. fig. 15. 



Three of those animals, being all entwined as in a common knot, first 

 one protruded its head to the right, then another to the left, and the third 

 unfolded itself between them. The whole three, as if by common consent, 

 extricated themselves, while the anterior portion of each advanced. 



Sometimes several individuals remained a long time thus implicated. 

 I have seen at least half a dozen, of different shades and dimensions, all 

 protruding the head from their complicated assemblage in different direc- 

 tions. Other animals, such as the Nereids, occasionally take refuge 

 among them with impunity. 



As long and unmanageable animals are frequently entangled among 

 corallines, or the refuse of miscellaneous matter, the mass should be de- 

 posited on an ordinary earthen or china white plate, with a clean flattish 

 shell in the vicinity, which, being discovered, they will crawl under it for 

 shelter. 



