ANN ULOID A SCOLECID A. 7 9 



classed with the Infusoria ; but the possession of a ner- 

 vous system and a complex digestive apparatus, en- 

 title them to a much higher place 

 in the animal kingdom. Some 

 place them among the Annelida; 

 other observers consider them allied 

 to the Insecta and Crustacea. They 

 have been placed among the Sco- 

 lecida, on account of the "water 

 vascular system" which they pos- 

 sess. Their nervous system is also 

 very different from anything found 

 in the Annulosa. 



The body is covered with a mem- 

 branous transparent skin, through 

 which the internal organs can be 

 accurately observed. Most are free 

 swimming; but some are attached 

 to aquatic plants, &c. The anterior 

 part of the body is furnished with 

 one or two discs surrounded by 

 cilia, which move so rapidly as 

 to produce the optical illusion of FIO. SS.-ROTIFERA. 

 rotating wheels. Early observers believed that they 

 really did rotate. The movements of these cilia, by pro- 

 ducing currents in the water, bring supplies of those still 

 more minute Infusoria on which the creatures feed. In 

 the free swimming species they also form organs of loco- 

 motion, acting like the screw of a steamer. The body is 

 shaped like a spindle or barrel. The lower extremity is 

 furnished with a tapering foot-like organ, with many 

 joints, which are capable of being sheathed one within 

 another like a telescope. The "foot" either terminates 

 in a sucking-disc, or is furnished with a pair of " toes." 

 In either case it is able to attach itself to some object 

 when it desires to become stationary. 



111. Digestion. As already mentioned, these animals 

 are provided with very effective food-bringers the cilia, 



