VOl l909^ *] Towns end, Use of Wings and Feet by Diving Birds. 247 



posterior and anterior extremity respectively. Where either 

 habit is not firmly established we should expect at times a return 

 to the primitive method, and we should expect to find it in young 

 birds. This is well shown in the case of the Loon. We should 

 expect to find it at all times in beginners in the art of diving, i. c, 

 among birds whose ancestry in the diving line is not a long one. 

 The Mallard, the Black Duck, the Gallinule, the Spotted Sand- 

 piper and the Water Ouzel may perhaps illustrate this contention. 



In conclusion the following tentative inferences from these 

 preliminary studies may be set down. 



1st. That progression by both the wings and feet under water 

 in diving birds is the primitive method, and is therefore to be looked 

 for among beginners and young birds. 



2d. That specialization towards the use of the wings alone leads 

 to a diminution in the size of the wings, and finally to a form of 

 bird that is flightless in the air; for wings of flipper proportions, 

 too small for aerial flight, are more efficient than large wings for 

 subaqueous flight, as witness the Great Auk and Penguins. 



3d. That specialization towards the use of the feet alone is 

 probably best adapted for the most rapid progression under water, 

 and this method may leave the wings undiminished in size for use 

 in the air. The apparent exception, Hesperornis, with powerful 

 feet but with wings degenerated to vestiges through disuse, serves 

 but to confirm the inference of the superiority under water of feet 

 action alone. 



References. 



1. Beebe, C. W. The Bird: Its Form and Function. New York, 1906, 



p. 4. 



2. Darwin, Charles. Voyage of the Beagle. New York, 1871, p. 200. 



3. Evans, A. H. Cambridge Nat. Hist, Vol. IX, Birds, London, 1900, 



p. 52. 



4. hoc cit., p. 54. 



5. hoc. cit., p. 56. 



6. Headley, F. W. Life and Evolution, 1907, p. 125. 



7. Kittredge, Joseph. The Wren. Bull. Norfolk Bird Club, I, 1909, p. 5. 



8. Lea, John. The Romance of Bird Life. London, 1909, p. 210. 



9. hoc cit., pp. 202, 203 



10. hoc cit., p. 211. 



11. hoc. cit., p. 203. 



