THE ROTIFERA AND THE RHIZOPODA. 681 



aquatic habits, it is evident, from many peculiarities of their formation, 

 that they deserve a much higher place, and in all probability constitute 

 a class by themselves. 



They are called Wheel Animalcules on account of a curious structure 

 which is found upon many of their members, and which looks very 

 like a pair of revolving wheels set upon the head. These so-called 

 wheels are two disc-like lobes, the edges of which are fringed with cilia, 

 which when in movement give to the creature an appearance as if it 

 wore wheels on its head, like those of the fairy knight of ballad poetry. 

 These wheels can be drawn into the body at will or protruded to some 

 little extent, and their object is evidently to procure food by causing 

 currents of water to flow across the mouth. All, however, do not 

 possess these appendages, but have a row of cilia, mostly broken into 

 lobes, extending all around the upper portion of the body. 



These remarkable beings are found mostly in water that has become 

 stagnant, but is partially purified by the presence of the infusorians, 

 which always swarm in such localities. 



The typical genus of this class is known by the name of Rotifer. 

 In all the members the body is rather elongated, and furnished at the 

 hinder end with a kind of telescopic tail, by means of which they can 

 attach themselves at will to any object, and release themselves when- 

 ever they please. Sometimes they move their bodies gently about 

 while still grasping by the extremity of the tail ; sometimes they are 

 nearly motionless ; while they frequently rock themselves backward 

 and forward so violently that they almost seem to be testing the 

 strength of their hold. 



These creatures can both swim and crawl, the former act of locomo- 

 tion being achieved by the movement of the cilia, and the latter by 

 creeping along after the fashion of the leech, the head and tail taking 

 alternate hold of the object on which they are crawling. The masti- 

 cating apparatus is always conspicuous, whether the animal has the 

 wheel protruded or withdrawn. It is situated behind the bases of 

 the wheel-lobes, and looks, when the animal is at rest, something like 

 a circular buckler with a cross composed of double lines drawn over 

 its surface. 



RHIZOPODA. 



The whole arrangement of the beings which we are now about to 

 examine is still very obscure, and the best zoologists of the present 

 time have declared that any system which has been hitherto adopted 

 can only be considered as provisional. 



These minute though beautiful beings exist in numbers that are ri- 

 valled only by the sands of the sea for multitude ; and the vast hosts 

 of these creatures can barely be estimated even when we know that 



