SELECTION 165 



sort between those that revived and those 

 that succumbed. General stability of struc- 

 ture was the essential characteristic of the 

 former. 



The fine researches by which the late Pro- 

 fessor Weldon proved discriminate elimina- 

 tion in shore-crabs, and by which Professor 

 Karl Pearson proved a selective death-rate 

 in man, are of the highest importance, but 

 they require more exposition than we can 

 give here. 



We may round off this section with two 

 simple observations whose picturesqueness 

 may emphasize our present point. 



Professor Davenport, of the Carnegie In- 

 stitution for Experimental Evolution, had 

 300 chickens in a field, 80 per cent, white 

 or black and conspicuous, 20 per cent, spot- 

 ted and inconspicuous. In a short time 

 twenty-four were killed by crows, but only 

 one of the killed was spotted. 



Finally, a kindred and recent field obser- 

 vation of our own. In a heavy snowstorm 

 at Johannesburg in August 1909, many 

 hundreds of trees were destroyed by the 

 weight of snow on the branches. It was 

 interesting, after the storm, to notice that 

 the elimination was in a marked degree 

 discriminate. The trees that suffered most 

 were the imported Australian trees, such as 



