VITAL PRINCIPLE. a7 
rals abound, while there are few examples of petrified fish. 
In the more recent strata, the remains of reptiles, birds 
and quadrupeds, occur, all of them differmg from the 
existing kinds. 
Attempts have been made to account for these cireum- 
stances by supposing, that the present races of animals and 
vegetables, are the descendants of those whose remains 
have been preserved in the rocks, and that the difference 
of character may have arisen from a change in the physi- 
cal constitution of the air, or the surface of the earth, 
producing a corresponding change on the forms of orga- 
nized beings. The influence of cultivation on vegetables, 
of domestication on animals, and of climate on man _ him- 
self, may be considered as strengthening the conjecture. 
But there are several difficulties which present themselves 
to those who adopt this opinion. The effect of circum- 
stances on the appearance of living beings, is cireumscri- 
bed within certain limits, so that no transmutation of species 
was ever ascertained to take place ;—and it is well known, 
that the fossil species differ as much, nay more, from the 
recent kinds, as these last do from one another. It re- 
mains, likewise, for the abettors of this opinion, to connect 
the extinct with the living races, by ascertaining the inter- 
mediate links or transitions. This task, we fear, will not 
be executed speedily. 
There is yet another view of the matter which suggests 
itself. If the seeds of some plants, and the eggs of certam 
animals, be so minute as to be excluded with difficulty 
from any place to which air and water have access, and if 
they are capable of retaining, for an indefinite length of 
time, the vital principle, when circumstances are not fa- 
vourable to its evolution, the crust of the earth may be 
considered as a mere receptacle of germs, each of which is 
ready to expand into vegetable or animal forms, upon the 
eccurrence of those conditions necessary to its growth. 
