24 PHILOSOPHY OF ZOOLOGY. 
aided by the infiuence of the sun, generated life in the less 
perfect organized beings, such as mushrooms and worms. 
This has heen termed Kquivocal or Spontaneous Genera- 
tion, and appears to have been devised by the Egyptians, 
to account for the hosts of frogs and flies which appeared 
on the banks of the Nile, on the ebbing of its periodical 
inundations. It was adopted by Artsror.e, and still con- 
tinues to be supported by a few naturalists. 
We have already stated, that the origin of life by umi- 
vocal generation, is demonstrated by direct proof and 
powerful analogies. Nor is it at all difficult to give an ex- 
planation of those appearances on which the whole fabric 
of the theory of equivocal generation rests. 
In the case of plants, some have supposed that the 
growth of the fungi, the mushroom among dung, and 
the other parasitical plants which appear on putrid flesh 
and fruit, might be regarded as examples of the truth of 
this theory. But the microscope makes us acquainted 
with seeds of these plants, and experiments prove that 
these seeds are prolific. The characters by which the dif- 
ferent species may be distinguished, though minute, are 
permanent ; and individuals of the same species appear in 
a variety of situations, — circumstances these, not to be look- 
ed for, in beings generated by corruption, or formed from 
the fortuitous concourse of atoms. 
The animalcules which make their appearance in water 
in which vegetable or animal substances have been infused, 
seem at first sight to favour this ancient doctrine. But, in 
these cases, the species have determinate characters, exhi- 
bit always the same proportion of parts, and transmit their 
vitality to their descendants, after the manner of animals of 
larger growth. Is it probable, therefore, that if these ani- 
malcules were produced by the spontaneous aggregation 
On 
of particles contained in these infusions, that they should 
