74 G. F. C. SEARLE, M.A., F.R.S., ON THE 
hundred million years have elapsed since the red-hot stage. 
In one of these methods the mass of sodium in the sea is 
estimated as well as the mass of sodium carried to the sea in 
one year by the rivers. These data give us the time which has 
elapsed since rivers first began to flow. 
Now the connection between matter and animal or vegetable 
life is destroyed when the organism is exposed to a red heat, 
and thus, if the existing order of things had prevailed without 
interruption from the time when the earth’s surface was 
red-hot, there would be no living organisms on the earth at the 
present day. Hence we conclude that the creation of the first 
living things on the earth has occurred since the time when the 
earth’s surface was red-hot. 
It has been suggested that life first appeared on the earth 
in elementary forms carried hither on meteorites, but this 
is no explanation, for it merely pushes the difficulty one stage 
further back. 
§ 14. The History of Species.’ *The history, as far as it can 
be ascertained, of the various species of creatures now inhabiting 
the earth, is of very great interest on account of the light which 
it may shed upon the nature of those most complex parts of the 
universe. This history demands consideration in the present 
paper because some of the speculations which were current in 
the last century, regarding this history, were used as arguments 
against religion. It is still widely believed that those specula- 
tions are fully accepted by all intelligent persons, and it 
therefore becomes necessary to give a brief account of the 
results reached in recent years. 
The idea was at one time held, that each living species had 
been separately created, and that apart from small variations, 
such as occur in the height of men or in the colour of their hair, 
each species, whether living or extinct, is incapable of change. 
This idea involved acts of creation taking place at different points 
of time, and hence it was natural that some should suppose that 
all the creatures now living are descended in an unbroken 
succession,from those which first existed, and that there has been 
but one solitary act of creation of life. This idea, of course, 
requires the supposition that the present species are descended 
from those which are, in some cases, now extinct, and therefore 
required the further supposition that the descendants of living 
forms may differ greatly from their ancestors. 
* In this section I have been greatly helped by Mr. R. H. Lock’s book 
on Lecent Progress in the Study of Variation, Heredity, and Evolution. 
