INFUSORIA. 95 



of separation, D after its completion. Assuredly this is one of the 

 most "remarkable phenomena which the study of living beings can 

 present. " By this mode of propagation," says Dujardin, " an In- 

 fusorian is the half of the one which preceded it, the fourth of the 

 parent of that, the eighth of its grand-parent, and so on, if indeed we 

 can apply the terms father or mother to animals which must see in its 

 two halves the grandfather himself by a new division again living in 

 his four parts. We might imagine such an Infusorian to be an aliquot 

 part of one like it, which had lived years, and even ages before, and 

 which by continued subdivisions into pairs might continue to live for 

 ever by its successive development." 



This mode of generation, however, enables us to comprehend the 

 almost miraculous multiplication of these beings. The amount defies 

 calculation, if we wished to be at all precise. We may, however, 

 arrive at a proximate estimate of the number which may be derived 

 from a single individual by this process of fission. It has been found 

 that at the end of a month two Stylonichitz would have a progeny of 

 more than 1,048,000 individuals, and that in a lapse of forty-two 

 days a single Paramecium could produce more more than 1,364,000 

 forms like itself 



The prodigious number to which they would reach, if we were to 

 add the other modes of propagation, viz., by germs and by budding, 

 we dare not calculate ; it would only be necessary to place a single 

 germ of one of these microscopic animalcules in a favourable con- 

 dition for its development, in order to produce myriads of them in a 

 very few days. 



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

 considered by some possible that a fourth mode exists, to which its 

 partisans give the name of spontaneous generation. According to their 

 views, an Infusorian can be produced, without egg-germ or pre-existent 

 parent. It is quite sufficient, they say, to expose organic matter, 

 animal or vegetable, to the action of. the air and water at a suitable 

 temperature, in order to see this matter organise itself, and form itself 

 into living infusorial animals. 



Such is the general theory of spontaneous or heterogeneous 

 generation, on which so much has been written within the last ten 

 years. Amongst great investigators of this theory have been the 

 two French naturalists, MM. Pouchet and Joly. Their views have, 

 however, made little progress ; they have, on the contrary, met with 

 vigorous opposition from the generality of French naturalists, and 

 from most of the members of the Academy of Sciences of Paris, who 

 have raised their voices against a doctrine which, however possible, is 



