168 MICROSCOPY FOR BEGINNERS. 



They are readily to be found by fishing for them with 

 a dipper, as recommended for Rhizopods. as they are 

 fond of gliding over the soft ooze at the bottom of shal- 

 low ponds. If the collector will also sweep his dipper 

 under the lily leaves and among the submerged stems 

 of Nuphar, he will not be disappointed. 



The animal consists of a free-swimming, flexible, and 

 elongated body, the anterior extremity usually enlarged 

 to form what may be called the head, a slight constric- 

 tion behind this part constituting 

 the neck; the central portion of 

 the body is formed with convex 

 Fig.i32. chsetonotusiarns. lateral borders and a more or less 

 strongly convex back or dorsum, 

 this region being variously appendaged with spines or 

 scales, and suddenly narrowed to produce the posterior ex- 

 tremity, which is forked, and bears two conspicuous tail- 

 like prolongations. The lower or ventral surface is a flat 

 and nearly level plane extending the entire length of the 

 body. It bears one longitudinal band of cilia near each 

 lateral border, seldom more. The head is usually some- 

 what triangular, and formed of three or five rounded 

 lobes. It has two tufts of vibratile hairs on each side. 



The mouth is on the ventral surface of the head, and 

 under a moderate amplification seems to be a circular 

 opening, but with an objective of high power it will be 

 found to be somewhat complicated. 



The whole upper surface of the body is, in the differ- 

 ent species, covered with rounded papillae, scales, spines, 



