24 PHILOSOPHY OF ZOOLOGY. 



aided by the influence of the sun, generated life in the less 

 perfect organized beings, such as mushrooms and worms. 

 This has been termed Equivocal 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 AUISTOTLE, and still con- 

 tinues to be supported by a few naturalists. 



We have already stated, that the origin of life by uni- 

 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 

 of particles contained in these infusions, that they should 



