PREFACE IX 



In this new edition I must mention again the benefit I have 

 derived from the practical assistance of Mrs B. M. Luke (for- 

 merly Miss Jordan) over a period of many years. Mrs J. A. Spokes 

 has once more typewritten the whole book and helped me by 

 careful attention to detail throughout. Several colleagues have 

 given me valuable advice on particular problems. I must especially 

 thank Dr E. L. Bowen, Mr F. M. Brewer, Mr W. Llowarch, and 

 above all Dr L. M. Venanzi, who has generously put his know- 

 ledge of the chemistry of aluminium at my disposal. Any errors 

 must be attributed to myself alone, for my advisers have not seen 

 what I have written. Sir Alister Hardy has continued to support 

 cytological studies in the Department of Zoology at Oxford, and it 

 is a pleasure to acknowledge his help. 



JOHN R. BAKER 



Cytological Laboratory 

 Department of Zoology 

 University Museum 

 Oxford 



