BOOK II. 



GENUS I. 

 MONADS. 



[In the following descriptions, the first name is that given 

 by F. O. Muller : this, when followed by a star (*), or 

 another with the letter E. in parentheses, denotes the generic 

 name of the same creature, given by Dr. Ehrenberg, the 

 organic characters of which will be found in Book 111.] 



This genus of animalcules includes the smallest forms in 

 which a voluntary motion has been observ ed, even under 

 the most powerful Microscopes : this motion, until re- 

 cently, appeared to be the only property of life with which 

 they were endowed ; but the observations of Dr. Ehren- 

 berg demonstrate an organization equally perfect with 

 animated beings of much larger dimensions. Their 

 forms in general are simple, spherical, or cylindrical 

 masses, devoid of external members or processes* : the 

 mouth, which is with difficulty discerned, is a simple 

 oritice, not furnished with ciliae or hairs, (except in 



* My observations on the Monas punctum require a modification of this part 

 of the definition, oi removed out of this genus. 



