78 VERMES. 



latter feature, have rendered it difficult to credit that all were mutilated, 

 and that none were entire. 



Nevertheless, with animals so readily exposed to mutilation, and 

 whose reproductive faculties are so energetic, it is impossible to avoid 

 perplexities regarding their integrity. 



Some of the preceding specimens were preserved a long time with- 

 out any symptoms of regeneration ; yet their resemblance to the subjects 

 of this paragraph, with a spinous prolongation, is so close, that I must 

 almost consider the description of both only as provisional. 



Specimens distinguished by the caudal process, however, are not 

 nearly so common as the others, on the contrary, they may be accounted 

 rare. 



a. GORDIUS VIRIDIS SPINIFER. Plate XI. Fig. 1. 



Length about three inches ; head and body resembling those of the 

 Gordius minor viridis already described, the groove being very distinct. 

 The posterior extremity terminates in a retractile, spinous, or cartilagi- 

 nous prolongation, and equalling about a sixth of the length of the body. 

 Colour mountain green. 



The spinous prolongation is a spontaneous protrusion, that is, it can 

 be retracted completely, especially when the animal is at rest, and when 

 gliding along it is drawn out to the slenderness of a human hair, actually 

 becoming invisible from extreme tenuity without a lens, or being placed 

 on a black ground. This prolongation is very flexible, forms various 

 curvatures, and displays peculiar action independently of the body. 



PLATE XI. 



FIG. 1. Gordius viridis spinifer. 



b. GORDIUS PURPTTREUS SPINIFER. Plate XI. Figs. 2, 3, 4. 



Among several specimens there has been scarcely any other distinc- 

 tion than colour ; nor can I A r enture to specify what may be the dimen- 

 sions of the species. 



