ACKNOWLEDGEMENTS 



My grateful thanks are due to the following, who spent much time reading and 

 criticizing various parts of the manuscripts and proofs: 



E. H. Ashton, A. d'A. Bellairs, Q. Bone, B. B. Boycott, P. M. Butler, S. Crowell, 



D. H. Cushing, F. C. Fraser, R. B. Freeman, H. Greenwood, I. Griffiths, R. J. 

 Harrison, R. A. Hinde, K. A. Kermack, J. Lever, N. B. Marshall, D. R. Newth, 

 C. Nicol, F. R. Parrington, P. Robinson, A. J. Sutcliffe, H. G. Vevers, E. I. 

 White, M. Whitear. 



Thanks for permission for reproductions of illustrations are due to: 



G. C. Aymar, E. J. W. Barrington, J. Berrill, T. H. Bullock, A. J. E. Cave, 

 W. E. Le Gros Clark, E. Crosby, F. G. Evans, Helen Goodrich, A. Gorbman, 

 J. Gray, W. K. Gregory, W. J. Hamilton, J. E. Harris, L. Hogben, A. Holmes, 



E. Hoskings, W. W. Howells, J. S. Huxley, F. Knowles, D. Lack, N. A. Mackin- 

 tosh, G. H. Parker, A. T. Phillipson, R. J. Pumphrey, E. C. R. Reeve, A. S. 

 Romer, E. S. Russell, F. K. Sanders, A. H. Schultz, G. G. Simpson, N. Tinber- 

 gen, G. L. Walls, L. Waring, T. S. Westoll, E. I. White, F. F. Zeuner, 



and to the following publishers and other bodies: 



The American Museum of Natural History; Bailliere, Tindall and Cox; E. 

 Benn, Ltd. ; Biological Reviezvs ; the British Medical Journal; the British Museum ; 

 the Cambridge University Press; the Company of Biologists, Ltd.; Dodd, Mead 

 & Co.; Editors of the Ibis; Longmans, Green & Co., Ltd.; the Physiological 

 Society; Putnam, Ltd.; the Scientific Monthly; the Wilson Bulletin; the Wistar 

 Institute; Zoological Society of London. 



