viii PREFACE 



lives (" achromatic," etc.) ; since, however, these adjectives have 

 a totally different meaning and use in optics, they have been altered 

 to chromaiinic, etc., in so far as they relate to chromatin. New 

 terms used in this book are chromidiosome (p. 65, footnote), endosome 

 (p. 73), as an equivalent to the German Binnenkorper, and gregarinUla 

 (p. 169). 



In conclusion, it is the author's pleasant duty to return thanks to 

 those of his colleagues who have kindly rendered him assistance in 

 his task. He is especially indebted for much help and many 

 valuable suggestions and criticisms to Dr. H. M. Woodcock, whose 

 unrivalled knowledge of recent bibliography has been throughout of 

 the utmost assistance ; and to Dr. J. D. Thomson and Miss Muriel 

 Robertson for many helpful discussions upon matters of fact or 

 theory. Dr. A. G. Bagshawe, Professor J. B. Farmer, F.R.S., Mr. 

 W. F. Lanchester, Dr. C. J. Martin, F.R.S., and Dr. P. Chalmers 

 Mitchell, F.R.S., have kindly read through some of the chapters, and 

 have given valuable advice and criticism. In justice to these gentle- 

 men, however, it should be stated that they are in no way responsible 

 for any of the theoretical opinions put forward by the author. The 

 majority of the figures have been specially drawn, from the original 

 sources, or from actual preparations by Mr. R. Brook-Greaves and 

 Miss Mabel Rhodes, to both of whom, the author's best thanks 

 are due. 



LISTER INSTITUTE OF PREVENTIVE 

 MEDICINE, CHELSEA, S.W., 

 July I, 1912. 



