THE SHAPES OF BIRDS 
HE enormous and sudden advance made 
by zoological science in the latter half of 
the nineteenth century has been followed 
by a reaction. During the last ten or 
twelve years that particular branch of knowledge has 
made comparatively little progress. Darwin and 
Wallace completely revolutionized biology. They shed 
the light of the highest genius on the darkness which 
had hitherto brooded over the study of life. Their 
researches gave an enormous impetus to natural science. 
Nor were these the only stimuli. The theory of natural 
selection met at first with very bitter opposition on all 
sides. This opposition stirred up the Darwinians to 
new exertions. 
Unfortunately the opposition was very shortlived. 
The triumph of the theory of natural selection was as 
speedy as it was complete. It would, I believe, have 
been more profitable to biological science had the con- 
flict been of longer duration. Natural selection has 
won all along the line. It has proved itself able to 
explain a large number of phenomena, it has overcome 
a multitude of difficulties. Facts which were at one 
time urged against it are now held to be among the 
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