G. H. G. Perry for figure 27 ; A. P. "Whitehead for 

 Plate xrv, d. Mr. P. Disney has been kind enough 

 to read the proofs. In addition I have to thank 

 Mr. P. C. Gilson for some valuable criticisms, Mr. 

 F. H. Jeffery for help in some small experiments : 

 Messrs. Duckworth have very kindly allowed me 

 to reproduce several of the illustrations of my Life 

 and Evolution. The photographs (with the one 

 exception I have mentioned) are my own. Most of 

 them are now published for the first time, but 

 several have appeared in Britisli Birds, and three 

 in the Journal of the Aeronautical Society. The 

 Editors of British Birds and the Secretary of the 

 Aeronautical Society kindly permit me to use them. 



F. W. HEADLEY. 



Haileybury, 



March, 1912. 



