ROTIFERS. 233 



and, as Dr. C. T. Hudson remarks, has been studied 

 in thousands of specimens by many practiced observers 

 during the century and a half which has elapsed since 

 the animals were discovered, the va2\& Rotifer vulgaris 

 is not known. 



II. St^phanops (Fig. 164). 



There are several species of these pretty little Roti- 

 fera, all of which may be known as members of this 

 genus by the extension of the front of the lorica over 

 the ciliary disk, like the visor of a boy's cap. A not 

 uncommon species is shown by Fig. 164, in side view, 

 so as to exhibit the long bristle springing from the 

 back, and the curved visor 

 which, in the figure, looks 

 like a hook above the front- 

 al cilia, yet is, in front 

 view, a circular shield. 



This Rotifer is one of the Fig. i64.-St^phknops. 



nibblers. The mastax is 



protruded from the preoral aperture, which is near 

 the front of the lower flattened surface, and bites and 

 tears the food it meets with. The animal is often to 

 be seen gliding over aquatic plants nibbling as it goes. 



The lorica is thin and somewhat flexible, and it ex- 

 tends over the sides of the body, so as to give the Roti- 

 fer an ovate outline when seen from above or from be- 

 low. The bristle on the back is very movable and 

 flexible. 



In another species {^St. lamellaris), the lorica is pro- 

 longed at the posterior border into two lateral teeth. 

 In another (St. muticus), this part is without teeth, and 

 the dorsal bristle (seta or slender spine) is also ab- 



