INFUSORIA. 



97 



Monde de la Mer," " present yet another kind of decomposition. 

 If we approach the drop of water in which one swims with the barb 

 of a feather dipped in ammonia, the animalcule is arrested in its 

 movement, but its cilia continue to move rapidly. All at once, 

 upon some point of its circumference, a notch is formed, which 

 increases bit by bit until the whole animal is dissolved. If a drop of 

 pure water is added, the decomposition is suddenly stopped, and 

 what remains of the animalcule recommences its swimming move- 

 ments." (Dujardin.) 



Life is spread over Nature in such abundance that the smallest 



Fig. 28. Paramecium aurelia and its Parasites. 



Infusorian has often as its parasite a creature still smaller ; these in 

 their turn serving as "a dwelling and pasture ground/' to use 

 Humboldt's words, for still smaller animalcules, as represented in 

 Fig. 28 a being parasites in various stages of development ; />, the 

 larger animalcule on which they have established themselves. 



The Infusoria may be divided into two groups the Flagelliferous 

 Infusoria, those, namely, which are provided with flagella, and the 

 Ciliate Infusoria, namely, those provided with vibratile cilia. The 

 greater number of the Infusoria belong to the first group, which 

 comprehends many families ; our space limits us to the mention here 

 of a few typical forms only in each group, selecting those which 



