ACKNOWLEDGEMENTS 



I am grateful to the following authors and publishers for 

 permission to use figures and to quote from their publications: 



Professor G. Schramm for kindly providing the photograph 

 from which Fig. 2 was taken. 



Dr. S. Brenner and Dr. R. W. Home for kindly providing the 

 photograph from which Fig. 3 was taken. 



Academic Press for permission to quote from the article by 

 H. A. Krebs in Chemical Pathways in Metabolism. Vol. 1, edited 

 by D. M. Greenberg. 



Allen and Unwin for permission to quote from the article by 

 G. R. de Beer in " The evolution of the Metazoa " from the book 

 Evolution as a Process edited by J. Huxley, A. C. Hardy and E. B. 

 Ford. 



Cambridge University Press for permission to take the table 

 printed on page 112 from Comparative Biochemistry by E. Baldwin; 

 the table on page 2 from The Cambridge University Handbook; 

 and the quotations from Biochemistry and Morphogenesis by J. 

 Needham, and Growth and Form by W. D'Arcy Thompson. 

 Masson et Cie for permission to reproduce Figs. 7, 8, 9, 11, 12, 15, 

 and 16, from Traite de Zoologie edited by P. P. Grasse. 



McGraw Hill for permission to reproduce Figs. 25 and 27, 

 taken from The Invertebrates by L. H. Hyman, and also for 

 permission to quote from this work. 



Oxford University Press for permission to quote from E. Radl's 

 History of Biological Theories and to adapt Fig. 43 from The Horses 

 by G. G. Simpson. 



Charles C. Thomas for permission to quote from a paper by 

 H. A. Krebs published in the Harvey Lectures. 



John Wiley for permission to take the table on page 20 from 

 General Biochemistry by J. S. Fruton and S. Simmons. 



IX 



