PREFACE Xlll 



Cameron, Cushing, Dandy, Dendy, Dimitrowa, Eycleshymer, Favaro, 

 Foa, Gaskell, Globus, Goodrich, Grenacher, Harris, Haswell, Hill, C, 

 Howell, Huxley, T., Huxley, J., Izawa, Kiaer, Kappers, Kerr, Kishinouye, 

 Klinckostroem, Kolmer, Krabbe, Lang, Lankester, Leydig, Lereboullet, 

 L'Hermitte, MacBride, MacCord, Marburg, Nicholson, Nowikoff, 

 Parker, G. H., Parker and Haswell, Pastori, Patten, Penfield, Quast, 

 Rio de Hortega, Schwalbe, Spencer, Stensio, Stormer, Strahl and Martin, 

 Studnicka, Tilney and Warren, van Wagenen, Watson, Woodward, A. S., 

 Zittel. 



We desire, further, to gratefully acknowledge the help which we have 

 received from Professor Doris L. MacKinnon of the Department of 

 Zoology, King's College, London, and Dr. J. A. Hewitt, Lecturer on 

 Physiology and Histology, King's College, London, for permission to 

 make use of the specimens of Geotria and Sphenodon which belonged to 

 the late Professor Arthur Dendy, and specimens from the Department of 

 Histology from which some of the illustrations have been drawn. We 

 also wish to thank Professors A. Smith Woodward, D. M. Watson, and 

 W. T. Gordon, for valuable help with respect to references to literature, 

 and Mr. Walpole Champneys and Margaret M. Gladstone for assistance 

 in drawing some of the illustrations. 



We also wish to express our thanks to Mr. E. J. Weston, Mr. Charles 

 Biddolph, and Mr. Denys Kempson for the valuable assistance they have 

 given in the preparation of serial sections of embryos and microphoto- 

 graphs. Lastly, we would like to thank Miss Mil ward Smith and Miss 

 Mary Popham, who between them have typed the whole of the manuscript. 



R. J. G. 

 C. P. G. W. 



London, 



November, 1939 



