G. H. G. Perry for lee ; A. P. Whitehead for 
Plate xIv,p. Mr. P. Disney has been kind enough 
to read the proofs. In addition I have to thank 
Mr. R. 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 British 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. 
EF. W. HEADLEY. 
HAILEYBURY, 
March, 1912. 
vi 
