MEASUREMENT OF NATURAL SELECTION 533 



the next ten rears ought to see a material advance in our knowledge of 

 the least investigated of the Darwinian principles. 



Studies of Vertebrates. 



The relative ease with which large numbers of individuals can be 

 secured and observed is an ample explanation of the fact that prac- 

 tically all the studies of selective elimination have been made on in- 

 vertebrates. 



To Dr. H. C. Bumpus belongs the credit of the first effort to de- 

 termine whether the death rate among vertebrates may depend in some 

 degree upon the measurable physical characteristics of the individual. 

 Indeed, in the attempt to apply quantitative methods to the problem of 

 natural selection Bumpus 23 was a close competitor for priority with 

 Professor Weldon. His statement of the problem, like that of Pro- 

 fessor Weldon, is beautifully clear : 



A possible instance of the operation of natural selection, through the process 

 of elimination of the unfit, was brought to our notice on February 1 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 disqualified, 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 their more 

 unfortunate companions. 



Prom his measurements of various bodily dimensions Professor 

 Bumpus concluded that the birds which perished were actually differen- 

 tiated from those which survived. Some of the differences, however, are 

 so small that to the cautious statistician this attempt to measure the in- 

 fluence of a selective death rate on the type of a population of birds liv- 

 ing in a state of nature seems suggestive rather than finally conclusive. 



This must not be read as a criticism of Bumpus's work, for he not 

 only saw the problem and the possibility of applying the new methods 

 to it, but he also gave us the full results from an unusual opportunity. 



First and last, considerable has been written concerning natural 

 selection in man. Most of the arguments are purely general or specu- 



23 Bumpus, H. C, ' ' The Elimination of the Unfit as Illustrated by the Intro- 

 duced Sparrow, Passer domesticus," Biological Lectures from the Marine 

 Biological Laboratory, Woods Hole, 1908, pp. 209-226, Boston, 1899. For fur- 

 ther statistical constants calculated from Bumpus's data see a note entitled, 

 "A Neglected Paper on Natural Selection in the English Sparrow," Amer. 

 Nat., May, 1911. p. 314-318. 



