ELEVENTH LECTURE. 



THE ELIMINATION OF THE UNFIT AS ILLUS- 

 TRATED BY THE INTRODUCED SPARROW, 

 PASSER DOMESTICUS. 



(A FOURTH CONTRIBUTION TO THE STUDY OF VARIATION.} 

 HERMON C. BUMPUS. 



WE are so in the habit of referring carelessly to the process 

 of natural selection, and of invoking its aid whenever some pet 

 theory seems a little feeble, that we forget we are really using 

 a hypothesis that still remains unproved, and that specific 

 examples of the destruction of animals of known physical dis- 

 ability are very infrequent. Even if the theory of natural 

 selection were as firmly established as Newton's theory of the 

 attraction of gravity, scientific method would still require fre- 

 quent examination of its claims, and scientific honesty should 

 welcome such examination and insist on its thoroughness. 



A possible instance of the operation of natural selection, 

 through the process of the elimination of the unfit, was brought 

 to our notice on February i of the present year (1898), when, 

 after an uncommonly severe storm of snow, rain, and sleet, a 

 number of English sparrows were brought to the Anatomical 

 Laboratory of Brown University. Seventy-two of these birds 

 revived ; sixty-four perished ; and it is the purpose of this 

 lecture to show that the birds which perished, perished not 

 through accident, but because they were physically disquali- 

 fied, and that the birds which survived, survived because 

 they possessed certain physical characters. These characters 

 enabled them to withstand the intensity of this particular 

 phase of selective elimination, and distinguish them from 



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