Marvels of Pond-Life. 13 



Common Wheel-bearer, Rotifer vulgaris, a favourite 

 object with microscopists, old and young, and capable, 

 as we shall see, of doing something more interesting 

 than taking the crawl we have described. 



A higher power, say one or two hundred, may be 

 conveniently applied to bring out the details of the 

 inhabitants of our live box more completely j but if the 

 glasses are good, a linear magnification of sixty will 

 show a great deal, with the advantage of a large field, 

 and less trouble in following the moving objects of our 

 search. 



Having commenced our microscopic proceedings by 

 obtaining some Euglense, Vorticellse, and a Rotifer, we 

 are in a position to consider the chief characteristics of 

 three great divisions of infusoria, which will often 

 engage our attention. 



It is well known that animalcules and other small 

 forms of being may be found in infusions of hay or 

 other vegetable matter, and hence all such and similar 

 objects were called Infusoria by early observers. Many 

 groups have been separated from the general mass 

 comprehended under this term, and it is now used in 

 various senses. The authors of the ' Micrographic 

 Dictionary ' employ it to designate ' c a class of micro- 

 scopic animals not furnished with either vessels or 

 nerves, but exhibiting internal spherical cavities, mo- 

 tion effected by means of cilia, or variable processes 

 formed of the substance of the body, true legs being 

 absent." The objection to this definition is, that it 

 to some extent represents theories which may not be 

 true. That nerves are absent all through the class is an 



