VIBRIO TRIBE. 309 



Polype. The former is about an inch long, of a yellowish 

 gray colour, with seven tentacula or arms : the latter is 

 green, with about eight short tentacula. 



ORDER V. ANIMALCULES. 



This is a race of animated beings so extremely diminu- 

 tive, that very few of them are visible to the naked eye, 

 or at all discernible without the assistance of microscopes 

 or magnifying glasses. They are principally found in 

 water, in which some animal or vegetable matter has 

 been steeped. There are several tribes, but it will not 

 be necessary, in this place, to speak of more than two ; 

 viz. the vorticella and vibrio tribes. 



The VORTICELL^E, or Wheel Animalcules, are very mi- 

 nute ; several of the species are found in stagnant waters, 

 and one of them, the Common Wheel-animal, in leaden 

 gutters, where the water has left a reddish sediment. 

 These are equal in size to a small grain of sand. On their 

 upper part there are two organs, which, after having fixed 

 themselves by the tail, they whirl rapidly round, for the 

 purpose of conducting food to their mouth. These crea- 

 tures are capable of very surprising changes of theirshape, 

 Sometimes they are of a lengthened form, sometimes 

 globular, sometimes contracted in the middle, appearing 

 as if divided into two parts, or shaped like a club, a tube, 

 or a cup. 



The animals of the VIBRIO TRIBE are thread-shaped, 

 and extremely minute. The species that are perhaps the 



