214 BIOLOGICAL LECTURES. 



tive development is evidently a mark of inferiority, and we are 

 justified in concluding that the birds so handicapped failed to 

 pass one of Nature's rigorous tests and perished. 



In an earlier lecture, on the " Variations and Mutations of 

 the Introduced Sparrow," facts were adduced which, it was 

 claimed, were sufficient to show that the English sparrow, since 

 its introduction into this country, has found life so easy that the 

 operation of natural selection has been practically suspended, 

 and that the American type consequently has become degen- 

 erate. No active agent had eliminated anomalies, and certain, 

 "freaks " had increased in number, until they had become over 

 four times as numerous as in England. 



When calling attention to the occurrence of these variations, 

 and to the fact that they were an indication of the absence of 

 an active eliminative factor, I little thought that within a few 

 months I might witness the action of an eliminating factor that 

 would test the structural qualifications of all the birds : destroy 

 those which had departed unduly from the ideal type, and thus 

 raise the general standard of excellence. 



It will be recalled that, after the storm of February i, one 

 hundred and thirty-six birds were taken, and that, of these, 

 seventy-two revived, while sixty-four failed to recover. But 

 the fact that the birds which perished had in the average 

 longer and larger bodies, and shorter head, wing, and leg 

 bones, does not tell all the story of selective elimination. 



Reference to the tables will show, not only that the longest 

 bird perished, but also that the shortest bird perished. The 

 longest bird was No. 33, the shortest No. 40. (In these and 

 other cases of extreme departure from the mean, the exponent I 

 is placed in the table beside the number of the bird.) 



Again, if we examine the columns of figures which indicate 

 the alar extent of the different birds, we find that both the bird 

 with greatest spread of wings, No. 32, and the one with least 

 spread of wings, No. 52, perished. 



The heaviest bird, No. 23, weighed 31 grams; it perished. 

 The honors for lightness are evenly divided; No. 53, among 

 the survivors, and No. 60, among the eliminated, have the 

 same weight, vis. t 22.6 grams. 



