X ACKNOWLEDGEMENTS 



Chas. J. Branford, Co. (Fig. 3-3). 



Butterworths Scientific Publications (Figs. 5-14, 5-23). 



Cambridge University Press (Figs. 3-1, 3-5, 3-6, 3-14, 3-16, 

 3-20, 3-21, 3-22, 3-24, 5-1, 5-2, 5-3, 5-12, 5-13, 5-16, 5-20, 

 5-24, 5-25, 5-26). 



Professor I. Chester Jones (Figs. 5-12, 5-13, 5-20, 5-24). 



Colston Research Society (Figs. 5-14, 5-23). 



Company of Biologists (Figs. 2-ld, 2-4, 5-1, 5-2). 



Council of the Marine Biological Association of the United 

 Kingdom (Figs. 3-1, 5-3, 5-26). 



D. C. Heath & Co. (Fig. 5-8). 



Koninklijke Vlaamsche Academic voor wetenschappen, Brussels 

 (Fig. 5-11). 



Marine Biological Laboratory, Wood's Hole, Massachusetts 

 (Figs. 2-lc, 2-5, 2-7, 2-9b, 3-2, 3-12, 3-15, 5-4, 5-7). 



Masson et Cie. (Figs. 2-le, 2-9a). 



Oxford University Press (Figs. 2-ld, 2-4). 



Springer Verlag (Figs. 2-lb, c, g, 2-2, 3-9, 3-10, 3-11, 5-18, 

 5-19). 



Stazione Zoologica, Naples (Fig. 2-6). 



Charles C. Thomas (Figs. 2-14c, 2-15). 



University of Chicago Press (Figs. 5-5, 5-17). 



Verlag Birkhauser (Fig. 2-3). 



Wistar Institute of Anatomy and Biology, Philadelphia (Figs. 

 3-13, 3-17). 



I am most grateful for the skill and understanding co-operation 

 of Mr. W. R. B. Buchanan and his staff in redrawing many of 

 these figures and interpreting my sketches; and for the clear 

 photographs of my drawings, taken by Mr. Ken Wood, for 

 Figs. 2-1 {a-f) and 2-14. I also wish to thank Miss J. McKinney 

 for her help in completing the indices and not least Mrs. P. M. 

 Richards for her unstinted help and encouragement in the prepara- 

 tion of the typescript and the main part of the indices, and in 

 correction of the proofs. Finally it is a pleasure to acknowledge 

 my indebtedness for the many facilities aflForded me by the 

 Director and Library staff of the Marine Biological Laboratory, 

 Plymouth, as well as by the staff of the Zoological Department 

 at Bristol. 



