THE SEQUOIA 
Rapid strides were made also in systematic zodlogy and in 
zo0-geography. The relations of the lower animals were worked 
out by Leuchart, Vaughn Thompson, Dujardin, Agassiz and a 
host of others. 
Expeditions were sent out to explore the earth and the sea. 
Famous among these are the voyage of the ‘“‘ Beagle,’’ on which 
Darwin served and did some of his earliest biological work; and 
the voyage of the * Rattlesnake,”’ on which Huxley was Assistant 
Surgeon. 
In 1859 Darwin published his “Origin of Species,” a book 
which is universally admitted to have had more influence on 
human thought than any other work of the century. 
Darwin's theory of the “Origin of Species’”” may be stated 
briefly as follows: All species tend to vary. No two individ- 
uals of the offspring of a pair are exactly alike. On account of 
this variation in structure or function, certain individuals are 
better able to thrive than their fellows. These animals transmit 
these characters to their offspring, which in turn survive in the 
struggle with their fellows. Thus nature eliminates those varia- 
tions which are disadvantageous to the organism, each individual 
being tested in its struggle to maintain its existence. The ac- 
cumulation of these favorable variations through many genera- 
tions is supposed to produce an organism quite different from 
the original stock, or, in other words, a new form. 
Few works have been constructed with more care and skill. 
For twenty years Darwin collected facts from all available 
sources, and made innumerable observations himself. The evi- 
dence in support of his theory was drawn from all branches of 
natural science: comparative anatomy, embryology, palzon- 
tology and zo6-geography. So numerous were the facts that he 
presented, and so careful was the exposition of his theory, that 
in less than twenty years it became the working hypothesis of 
nearly every biologist. 
Long before Darwin's time the resemblance between groups of 
animals had been recognized, and many new facts made known 
by investigators from Vesalius onward emphasized these resem- 
blances. In 1620 Bacon published “* Novum Organum,” in which 
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