ZOOLOGT. 269 



ORDER V. 



INFUSORIA. 



The subjects of this order are all exceedingly minutej being 

 for the most part only discoverable by the Microscope; 

 they are found in stagnant watercj vegetable infusions, and 

 are generally knowu by the terra Animalcules . They are 

 divisible into three families : * with external organs : **with- 

 o\xt external organs, Q.&tteneA: ***• vfithoixt external organsj 

 round. 



1. Brachhnus. Body contractile, covered with a shell, 



and furjij^hed at the head with cllirited rotatory organs. 



2. Vorticella. Uof?^ contractile, naked, and furnished with 



ciliated rotatory organs ; this genus is divided into three 

 families; "■ animal affixed on a. stem or pedicle; ** 

 animal isikd ; **^ animal without stem or tail. 



Most of this genus are so miuuta, as not to be discover- 

 able without the aid of a lens. 



3. Trichoda. Animal minute, pellucid, hairy or horned ; 



there are two families in this genus, the one hairy, the 

 other with horn-like processes. They are all micro- 

 scopic objects, and invisible without the assistance of 

 glasses. 



4. Cercaria. Animal invisible to the naked eye ; pellucid 



and tailed. 



