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 Stylonichie 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 
