142 DEOPS OF WATER. 



large, comparatively speaking, a glass magnifying 

 250 diameters is quite sufficient to see them with 

 perfect ease. I shall only describe a few of the 

 most common genera, referring the student to 

 Ehrenberg's or Pritchard's excellent works, 

 where each species is minutely described, and 

 as ably illustrated as means will allow. 



One of the first genera of the Rotatoria, 

 though it will not be the first to attract the atten- 

 tion, is a creature somewhat resembling a long 

 narrow fish with a forked tail. The IchtJtydium 

 podura has a transparent, colourless body, long, 

 and constricted so as to form a head ; it swims 

 rapidly, but is generally seen creeping : the tail is 

 formed of two parts, like a pair of pincers. 



The next genus, Chtetonotus, is more common, 



