INFUSORIA. 



105 



by this process of fission. It has been found that at the end of a 

 month two 8tyloniclii& had a progeny of more than one million and 

 forty-eight thousand individuals, and that in a lapse of forty-two days 

 a single Parameoium had produced more than one million three 

 hundred and sixty-four thousand forms like itself. 



Life is spread over Nature in such abundance that the smallest 

 infusoria has its parasite a little 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. 29 a being parasites 

 in various stages ; I, the larger animalcule on which they have estab- 

 lished themselves. 



a 



Fig. 29. Paramecium aurelia and its Parasites. 



The prodigious number to which the calculation would reach, if we 

 were to add the other modes of propagation, viz., by germs aud :by 

 budding, we dare not mention : it would only be necessary to place a 

 single germ in a favourable condition for its development, in order to 

 produce myriads of these microscopic animalcules in a very few 

 days. 



We have seen three modes of reproduction in the Infusoria ; it is 

 possible that a fourth mode exists, to which its partisans give the 

 name of spontaneous generation. According to their views, an 

 infusoria can be produced without egg-germ or pre-existent parent. 

 It would be sufficient to expose organic matter, animal or vegetable, 

 to the action of the air and water at a suitable temperature, in order 



