No. 381.] A HALF-CENTURY OF EVOLUTION. 627 
complex of facts, and enables us to make predictions, the true 
test of a scientific theory. Biology is not an exact science, 
hence the theory is not capable of demonstration like a prob- 
lem in mathematics, but is based on probabilities, the circum- 
stantial evidence being apparently convincing to every candid, 
well-trained mind. 
The methods and results of natural science, based as they 
now are on evolutional grounds, have, likewise, appealed to the 
historian, the philologist, the sociologist, and the student of 
comparative religion, whose labors begin with investigations 
into the origins. 
It goes without saying that, thanks to the initiative of the 
above-named zodlogists, every department of intellectual work 
and thought has been rejuvenated and rehabilitated by the 
employment of the modern scientific method. All inquiring 
minds appreciate the fact that, throughout the whole realm of 
nature, inorganic as well as organic, physical, mental, moral, and 
spiritual, there was once a beginning, and that from a germ, 
by a gradual process of differentiation or specialization, the com- 
plex fabric of creation has, by the operation of natural laws and 
forces, been brought into being. All progress is dependent on 
this evolutionary principle, which involves variation, adaptation, 
the disuse or rejection of the unfit, the use or survival of the 
fittest, together with the mechanical principle of the utmost 
economy of material. 
Though the human iind has its limitations and the chief 
arguments for evolution have been drawn from our observations 
of the history of our own planet and of the life existing upon 
it, the nebular hypothesis teaches us that the same process 
has determined the origin of other worlds than ours, and applies 
in fact to all the other members of our solar system, while with 
little doubt the principle may be extended to the entire universe. 
At all events, evolutionary modes of thinking have now 
become a second nature with philosophic, synthetic minds, and 
to such any other view is inconceivable. We teach evolution in 
our colleges and universities, and the time is rapidly approach- 
ing, and in some instances has already come, when nature 
Studies and the facts of biology forming the grounds of the 
