INTUSOEIA. 473 



which they touch is in focus, is very curious. They 

 are rapidly moved, but without regularity; the tips 

 bend as they touch the surface of the glass ; some 

 of them seem to have accessary hairs, equally long, 

 but slender, proceeding from the same base. On the 

 hinder quarter of the ventral surface are several thick 

 pointed spines ; these are inflexible, nearly straight, 

 placed side by side, but not in regular order, some 

 reaching beyond others. I have not seen these used, 

 but they commonly remain sticking out in a horizontal 

 direction. These organs are termed sl/yles. Besides 

 these, there are three slender bristles, called set(B, 

 placed at the hinder extremity, the central one in the 

 line of the body, the others radiating at an angle. 

 These are distinguished from the cilia, not only by their 

 length, but by not being vibratile. The motions of 

 these animals are powerful, but irregular and fitful, 

 very much like those of the former species. They dart 

 hither and thither, backward as well as forward, oc- 

 casionally shooting round and round in a circle, 

 with many gyrations, much like the pretty little 

 polished beetles {Oyrinus) that play in mazy dances on 

 the surface of a pool. The two extremities seem 

 covered with minute pits or stipplings, but colourless ; 

 the central part is occupied with yellowish granules of 

 different sizes. 



I once witnessed the dissolution of one of these 

 animals under peculiar circumstances. Two or three 

 stems of an aquatic plant had become crossed in the 

 live-box so as to form an area, into which the Stylony- 

 chia had somehow introduced himself. There was just 

 room for him to move backward and forward without 

 turning, and the space was about three times his own 



