88 



DESCRIPTION OF 



[Poli/gasfrica. 



diameters, together with considerable penetration and a 

 good definition. 



The family comprises forty-three species, distributed 

 among nine genera, as follow : — 



Swimming 



Eye wanting 



Eye present 



r Single Monas. 



Voluntarily Uvella. 



Aggregate During | p,,^,,^,. 



^ 



Single 



Proboscis 

 one or two 



[■ Microglena. 



Proboscis 1 „, , 



many ; Pl^acelomonas. 



''Aggregate Glenomorum. 



\ Rolling Doxococcus. 



Lips present Chilomonas. 



Tail present Bodo. 



Genus I. Monas. The Monads. — -The animalcules of 

 this genus — the true Monads — are described (see the Table) 

 as being deficient of the eye, projecting lip and tail, and 

 always swimming in the direction of the longitudinal axis 

 of the body, their mouth being situated at the anterior 

 part. It is another distinguishing character of the true 

 Monad that it is never seen to cluster with others of its 

 genus, so as to form a berry-like mass, and hence it is 

 designated single, in contradistinction to aggregate. At 

 present, there are twenty-six species of this genus known — 

 two green, two yellowish, three inclining to red, and the 

 remainder colourless; but it should be mentioned, that 

 although there be colour, it must not be regarded as a 

 characteristic to be entirely relied upon. Monads may 

 often be present in water, under inspection, without being 

 seen, through the want of a competent magnifying power; 

 you would seek for them in vain with a power less than 



