374 On Spontaneous Generation. 



different climates, which are like so many islands amidst wide 

 tracts of neptunic formations. Could the seeds of plants cha- 

 racteristic of these localities, have been brought there from the 

 ignited bosom of the earth ? Or can the more recent volcanic 

 localities have received theirs from others, with which they 

 have no hydrographic communication ? When the bottom of 

 the sea, or of a lake, was laid dry, either by sudden elevation 

 or gradual exsiccation, there were likewise created breeding- 

 grounds for the spontaneous generation of animals and plants 

 peculiar to those localities, according to the nature of the 

 ground and climate. Even some of the modifications of mat- 

 ter effected for the first time by man, may, within the histo- 

 rical times have given rise to animals and plants not existing 

 before. But as volcanic eruptions, piercing through the stra- 

 ta of the present epoch, the change of the localities of seas 

 and lakes into dry land, as well as the other incidental modi- 

 fications of the surface of the globe, are, at the period in which 

 we live, for the greater part, if not altogether, repetitions of 

 what has happened many times before ; as, moreover, we are 

 so distant from the great creative period of our epoch, we can- 

 not expect to see new species of animals or plants rise from 

 the ground, though many circumstances appear to prove that 

 the spontaneous generation of plants of the species already 

 existing, is still actively going on ; whereas the series of the 

 organic creation of the present epoch, may be considered as 

 complete, or perhaps very nearly so. 



With the undeniable cases of spontaneous generation in the 

 human body before us, we shall not hesitate to ask any unbi- 

 assed man, whether he can better understand how the 

 Pediculns capitis humani is generated from the integuments 

 of the human head, than how an elephant could spring from 

 the materials of the earth and atmosphere, of which he is com- 

 posed, under all the predisposing circumstances ? The an- 

 swer will be unanimously in the negative, but at the same 

 time everybody, I think, must allow, that the two cases are 

 perfectly analogous, and the conclusion to which this must 

 necessarily lead, is, that even if no direct proof can be brought 

 forward for the generatio aquivoca being a general law of na- 

 ture, the denial of it would be altogether unphilosophical. 



That the aboriginal organisms of each locality owe their 

 existence, and peculiar type and structure, to the local condi- 

 tions of each part of the surface of the globe, becomes suffi- 

 ciently clear from the strict adaptation of the animals and 

 plants to their habitats, and to each other in each habitat ; 

 which principle is the more evident, the better any locality is 

 defined and insulated. There are countries where the simi- 



