342 



ACTION OF NATURAL SELECTION 



perished. On comparing the survivors with the elimi- 

 nated individuals, very appreciable differences were 

 found to exhibit themselves. The means of the values 

 obtained with all the birds, both male and female, are 

 given in the accompanying table : 



Here we see that the average characters differ but 

 little. The eliminated individuals are 1.27 per cent, 

 greater in length, and 2.38 per cent, greater in 

 weight, whilst they are about 1 per cent, smaller 

 than the survivors in respect of most of the other 

 characters measured. The variability, or range of 

 variation of the eliminated birds about their mean, 

 is, however, very much greater than in the case of the 

 survivors. Of the nine characters measured, the varia- 

 bility is greater in eight, the average excess being no 

 less than 18.8 per cent. The variability was less in re- 

 spect of the sternum alone, and then only by 3.1 per 

 cent. In the accompanying figure are given curves of 

 distribution of the lengths of the surviving and of the 

 eliminated birds. It is obvious that the dotted line 



