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 bnrb 

 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 





a 



'-///'iiliihuV'"' 

 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; b^ the 

 larger animalcule on which they have established themselves. 



The Infusoria may be divided into two groups — the Flagelliferous 

 Lifusoria^ 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 



H 



