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THYOXES. 



covered with fragments of shells and corallines, which were 

 evidently retained by the suctorial property of the papillae, 

 and the animal, on being kept a day in sea- water, threw 

 them off. It had a slow progressive motion ; slower than the 

 shadow of the dial, which was effected by elongating the 

 papillae of one part, fixing them to the plate, and then 

 drawing itself forward by again contracting those elongated 

 parts ; but the papillae were oftener used for the purpose 

 of anchors than of feet, the creature being of an indolent 

 and immoveable character. When stationary, it was ever 

 slowly changing its outward form ; it was now shortened 

 and swollen in the centre ; then it would relax itself and be- 

 come cylindrical ; again one part would be blown out, and 

 another drawn in with a deep stricture, as if a thread had 

 been tied round ; or again the contraction would begin 

 near the head, which is then made very narrow, and would 

 spread backward, the anterior portion recovering its ori- 

 ginal diameter as the wave of constriction passed away ; 

 and sometimes the constriction will spread in the opposite 

 direction. It often raised the posterior extremity a little 

 from the surface of the plate, and to one side ; but I never 

 saw any current flow from the aperture. To effect these 

 varied motions, we must suppose the existence of muscular 

 bands or fibres on the coriaceous skin, both in a longi- 

 tudinal and circular direction ; and on opening the body 

 we find such to be the case : five strong, white, raised 

 bands run from one end to the other, radiating from the 

 circular apertures, and numerous fibres pass between them 

 transversely, among which minute pores open everywhere, 

 which are the inner orifices of the cuticular papillae." Dr. 

 Johnston adds the following account of the voluntary 

 ejection of its viscera : — " The worm having been kept in 

 sea- water, unchanged for two or three days, sickened, and, 



