SUPPLEMENT 
ON THE 
INFUSORIA. 
ON these curious beings, of which so little is known, and 
whose place in the living series is so far from being deter- 
mined, we cannot pretend to offer any thing more than a few 
general observations. 
The denomination of INFUSORIA, was introduced into 
zoology by Otto-Frederic Miiller, to designate a class of 
animals which are developed in vegetable or animal infusions, 
and which, from their extreme smallness, have also been 
named microscopic. All systematic authors since Gmelin, 
have adopted the division and the name, though some have 
rather restrained its application, and others, in admitting it, 
have observed that it was very badly circumscribed. In fact, 
Miiller was guided by no principle in the establishment of 
this class, and it is therefore probable that it contains an 
anomalous assemblage of animals of degrees of organization, 
or types, extremely different, and equally different degrees of 
development. The only common characters which they pos- 
sess, if characters they can be called, are their extreme lit- 
tleness and transparence, which render them appreciable 
only by the microscope; their constant habitat in a fluid, 
13 
