THE ELIMINATION OF THE UNFIT. 213 



Test 7: LengtJi of Femur. An examination of the general 

 averages on Tables III and III a shows that the survivors pos- 

 sess longer thigh bones than do the birds which succumbed. 

 The average length of femur in the former is .716 inch ; in the 

 latter .709. This difference in the averages cannot be ascribed 

 to the large number of dead females, since the difference pre- 

 vails also for both the adult and young males. 



Test 8 : Length of Tibio-Tarsus. Measurement of the tibio- 

 tarsus yields practically the same comparative data as the 

 measurement of the upper bone of the leg, although in both 

 groups of birds this bone in the females is considerably longer 

 than in the adult males, notwithstanding that the females are 

 smaller. This series of measurements agrees with the sixth, in 

 that the young males have longer legs than the adult males. 



Test q. Measurements across the skull, from the postorbital 

 bone of one side to the postorbital bone of the other, are given 

 in the eighth column, and are less satisfactory, perhaps, than 

 those of other portions of the skeleton. The breadth of the 

 cranium, as thus indicated, is somewhat less in the females than 

 in the males. The averages denote that the birds which sur- 

 vived had wider heads than those which perished, but these 

 averages are considerably influenced by data furnished by the 

 young males. The irregularities in the subordinate groups 

 induce me to place less confidence in these numerical results 

 than in the results from measurements of other structures. 



Test IO : Length of Sternum. This test differs from other 

 tests in that it relates to measurements in the longitudinal 

 axis of the body. In the males the sternum is long, and in 

 the females it is short. In the birds which survived it has a 

 general average length of .845 inch ; in those which perished 

 it has a general average length of only .834. 



I think these tests prove that there are fundamental dif- 

 ferences between the birds which survived and those which 

 perished. While the former are shorter and weigh less (i.e., 

 are of smaller body), they have longer wing bones, longer legs, 

 longer sternums, and greater brain capacity. These characters 

 are in accordance with our ideas of physical fitness ; their defec- 



