5 
can, to throw ridicule on Christianity, while another will give you 
a genealogical tree showing the ancestors of any species you like. 
And many of us are familiar with the brilliant articles of Grant 
Allen in the interests of the theory, in which he will commence 
with an ‘‘ if,” or a ‘* suppose,”’ and then building on this supposi- 
tion, triumphantly conclude with Q.E.D. 
What then is this Theory of Development? I will make my 
account as short as 1s consistent with lucidity. 
Everything on the earth, the earth itself, is ina state of constant 
change; rest.and stability are nowhere to be found. Mountains 
and seas alike disappear in time; summer becomes winter, and 
winter summer; the climate of a hemisphere changes with the 
lapse of ages. We dig up here in England the fossil remains of 
palms, cinnamons, figs, and Wellingtonias which onee grew round 
its old lakes ; we find stores of coal embedded in ice on the shores 
of the Polar Sea; the elephant and hippopotamus once fed on this 
very spot, and the reindeer has occupied the south of sunny France. 
With all physical changes, of land and water and climate, the 
animal and vegetable world must change too, not only their 
localities. but also in their structure and habits. Any species 
unable to adapt itself to altered circumstances must disappear. It 
is the riddle of the Sphynx, then, now, and ever—‘‘ Do this or 
perish.”” When the climate of England was at one time sufficient 
for the semi-tropical trees just mentioned, and at another was such 
that every mountain top was swathed in ice, and every valley sent 
out its glacier as the valleys of Switzerland do now, the species 
suitable for the former period could not exist in the latter. Con- 
sequently they disappeared. And a fresh fauna and flora were 
established in their stead. This explains the occurrence of the 
remains of totally extinct animals. The same work is still in 
progress. The Gair-fowl has disappeared from the earth within 
the memory of living man, being convinced of the fruitlessness of 
its struggle for existence. The earth is no longer fitted for it. 
Now the point in question is—How did the animals, new to the 
earth, come into existence? Was there a total destruction of one 
ancient world of life, and a totally new and sudden creation of 
another? This was the belief of the early geologists. Or did new 
forms yradually put in an appearance, being gradually created (i.e. 
developed) out of the old ? coming in so slowly stepwise that no 
one could ever say when the old form was succeeded by the new. 
Tbis latter view is what we are considering this evening ; it is this 
idea which has beer so industriously worked out by Wallace and 
Darwin. 
If one thing is more certain to the geologist than another in his 
_ Studies it is this,—that since the appearance of the first form of 
