Monadina.'] infusorial animalcules. 135 



"with a posterior variable process in the form of a tail, of greater 

 or less length and fineness. 



The Cercomonads differ from the Monads in the postei'ior pro- 

 longation, serving by the adhesion of its extremity as a point of 

 support, and which is either elongated as a very fine thread, or con- 

 tracted into a small tubercle. It is sometimes nearly as fine at the 

 anterior filament, and susceptible of an undulatory motion. 'I have 

 not unfrequently witnessed the transition of monads to the condition 

 of Cercomonads. 



"We may conclude that many of the animalcules described in the 

 genus £o(h, (Ehr.), are examples of this genus Cerconionas, Duj., 

 although sufficiently marked characters are wanting, in order to dis- 

 cover special identity. 



Cycliditjm detracta. — Body discoid, or oblong, granular, with a 

 thick tail. Length 1 -7000th., 1 -2300th. 



C. crassicanda. — Body elongated, nodular, flexible or variable form, 

 more or less contracted posteriorly into a tail. Length l-3400Lh, 

 1 -2600th. 



C. viridis. — Body ovoid, oblong, tubercular, green, prolonged pos- 

 teriorly into a tail of vai'j'ing tenuity, or into a rounded lobe, or 

 spatidate expansion. Length l-1500th. 



C. lacryma. — Body globular, uneqxial, elongated posteriorly, as a 

 long, flexuose tail. Length of body l-5200th., l-3000th. Length 

 of tail l-2600th. Length of filament 1 -750th. 



C. accuminata. — Body globular or ovoid, contracted posteriorly 

 into a short tail, terminating by a veiy fine filament. Length 

 l-2600th., l-1900th. 



C. glohiiJosus. — Body globular, with a filament at each exti-emity 

 doiible its length, the anterior one, more actively moved. Length 

 1 -2600th. Found in marsh water. 



C. longicmida. — Body fusiform, flexible, terminated posteriorly by 

 a long and very slender filament, also flexuose. Length of tail 

 l-1800th. 



C. fusiformis. — Body dilated at centre, constricted in front, and 

 prolonged behind into a long delicate tail. Length of body 

 ] -1900th. 



C. cyUndricm — Body cylindrical, elongated constricted posteriorly, 



