212 BIOLOGICAL LECTURES. 



young males, and females with females, we find that the 

 differences between the two classes of birds are expressed 

 in these three smaller divisions, and I think we are justified in 

 concluding that the differences are really significant. 



The explanation that the birds which lived were those which 

 sought, or at least enjoyed, better shelter cannot be entertained, 

 for the storm was of long duration, and the birds were picked 

 up, not in one locality, but in several localities ; and, moreover, 

 it is a fact that the survivors are structurally different from 

 those which perished. If to these structural characters one 

 desires to add also the intellectual character that the birds knew 

 enough to go in out of the storm, the difference between the 

 two groups becomes so much the greater. 



Test 5-' Length of Head. A comparison of the average 

 lengths of head, from the tip of the beak to the occiput, shows 

 only a similarity between the survivors and those which per- 

 ished, and indicates that under the present environmental 

 conditions this feature is not sufficiently prominent to be 

 expressed by this method of computation. 



Test 6: Length of Humerus. An examination of the fifth 

 column of figures will show that the length of the arm bones 

 of the birds which perished always averages less than that of 

 the survivors. This difference is most conspicuous in the adult 

 males, where the surviving birds have an average length of 

 humerus of .738 of an inch, considerably more than that of 

 their unfortunate companions, .727. 



Here again I wish to emphasize the fact that these differ- 

 ences cannot be merely accidental, because they so often tend 

 in the same direction. If among the survivors it is the proper 

 thing for adult males to have a long humerus, then the young 

 males have a long humerus, and the females follow the prevail- 

 ing fashion with characteristic servitude. If a short humerus 

 is an index of inferiority, all three groups of eliminated birds 

 (adult males, young males, and females) bear this same mark of 

 inferiority. This fact is the more striking since the averages 

 are established on a relatively small number of birds, while 

 usually in the statistical methods of the study of variation an 

 abundance of material is necessary. 



