The Making of Species 
sight of in the mental stagnation of the Middle 
Ages. In that dark period zoological science 
was completely submerged. It was not until 
men shook off the mental lethargy that had 
held them for many generations that serious 
attention was paid to biology. From the 
moment when men began to apply scientific 
methods to that branch of knowledge the idea 
of evolution found supporters. 
Buffon suggested that species are not fixed, 
but may be gradually changed by natural causes 
into different species. 
Goethe was a thorough-going evolutionist ; he 
asserted that all animals were probably descended 
from a common original type. 
Lamarck was the first evolutionist who sought 
to show the means whereby evolution has been 
effected. He tried to prove that the efforts of 
animals are the causes of variation; that these 
efforts originate changes in form during the life 
of the individual which are transmitted to its 
offspring. 
St Hilaire was another evolutionist who en- 
deavoured to explain how evolution had occurred. 
He believed that the transformations of animals 
are effected by changes in their environment, 
These hypotheses were considered, and rightly 
considered, insufficient to explain anything like 
general evolution, so that the idea failed for a 
time to make headway. 
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