420 BIOLOGY AND ITS MAKERS 
evolution, was unable to state explicitly what these causes 
were.” 
Darwin and Wallace.—In 1858 we come to the crown- 
ing event in the rise of evolutionary thought, when Alfred 
Russel Wallace sent a communication to Mr. Darwin, beg- 
ging him to look it over and give him his opinion of it. Darwin, 
who had been working upon his theory for more than twenty 
years, patiently gathering facts and testing the same by 
experiment, was greatly surprised to find that Mr. Wallace 
had independently hit upon the same principle of explaining 
the formation of species. In his generosity, he was at first 
disposed to withdraw from the field and publish the essay of 
Wallace without saying anything about his own work. He 
decided, however, to abide by the decision of two of his 
friends, to whom he had submitted the matter, and the result 
was that the paper of Wallace, accompanied by earlier com- 
munications of Darwin, were laid before the Linnean Society 
of London. This was such an important event in the his- 
tory of science that its consideration is extended by quoting 
the following letter: 
“Lonpon, June 30th, 1858. 
“My DeEaR Sir: The accompanying papers, which we 
have the honor of communicating to the Linnzan Society, 
and which all relate to the same subject; viz., the laws which 
affect the production of varieties, races, and species, contain 
the results of the investigations of two indefatigable natural- 
ists, Mr. Charles Darwin and Mr. Alfred Wallace. 
“These gentlemen having, independently and unknown 
to one another, conceived the same very ingenious theory to 
account for the appearance and perpetuation of varieties 
and of specific forms on our planet, may both fairly claim the 
merit of being original thinkers in this important line of 
inquiry; but neither of them having published his views, 
