126 INVERTEEEATE ANIMALS. 



are known as the " respiratory tubes '' {g g), and which terminate 

 near the anterior end of the body, apparently by blind extremities. 

 The nervous system is in the form of a large double ganglion placed 

 above the gullet, and having one or two eye-specks placed upon it. 

 The ovaries (o) constitute conspicuous organs in the female Rotifera, 

 but in summer the young Rotifers appear to be produced by the 

 females without having access to the males. 



The Rotifera were long confounded with the Infusoria, in conse- 

 quence of their great similarity in external appearance. They are, 

 however, fundamentally distinguished from the Infusorians by their 

 possession of a definite body-cavity, the presence of a well-developed 

 alimentary canal, and the possession of a nervous system and of 

 proper reproductive organs, while their development is also qviite 

 different. 



