ROTATORI.E. 



167 



are generally the Monads, which in a very short period increase to a 

 most extraordinary extent. These afterwards gradually decrease, larger 

 and more perfect creatures supplying their place, as the Peridinida, 

 Paramesia, Trachelina, Acineta, and others ; and these, again, are sup- 

 planted by the Vorticellse and Branchionsea. Though the generations 

 thus rise up, there is no regular order in their doing so, even in the 

 same infusions. 



THE ROTATORI.E, ROTATING OR WHEEL-ANIMALCULES. 



This higher grade of the Infusoria, now classed among the Articu- 

 lata, derives its name from the appearance presented by the motion of 

 its circles of cilia on the superior part of its body, which resembles the 

 turning round of a wheel, as they rapidly vibrate. Many have been 



fig. 101. 



1. The common Wheel- Animalcule, with its cilia or rotators pbinted. 2. The same 

 in a contracted state at rest : at g is seen the development of the eyes in the 

 young. 3. Pitcher-shaped Brachionus : a the jaws ; b the shell ; c the cilia, or 

 rotators ; d the tail. 4. Baker's Brachionus : a the jaws and teeth ; b the shell ; 

 c the rotators ; e the stomach. 5 and 6. Other forms of the same family, 



the speculations as to the mechanism of this beautiful movement : some 

 have considered it as a magnetic or electrical force; and as one passes 



