PREFACE 



IN parting with the present volume I have the satisfaction 

 of feeling that I have accomplished the first part of the 

 task which I set myself fourteen years ago. When I began 

 I looked forward to executing the whole work, both Special 

 and General Parts, myself in seven or eight years. That 

 expectation has not been realized. Indeed had it not been 

 for the assistance given me by my colleagues, Mr. J. J. 

 Lister and Mr. A. E. Shipley, the present volume would have 

 been far from completion. Thanks to their generous 

 co-operation it is now finished, and I am in a position to 

 turn my attention to the General Part. It is satisfactory 

 to have finished it, but it is impossible to avoid a feeling of 

 regret that owing to circumstances which were unforeseen 

 when the work was commenced it has occupied so many 

 years and that the General Part, to write which the Special 

 Part was undertaken, is not yet begun. 



The distribution of the work of this volume has been 

 as follows : The chapters on Tunica ta, Enteropneusta, 

 Echinodermata, Onychophora and Myriapoda are by my- 

 self ; the chapters on the Arthropoda in General and on 

 the Crustacea, and the section on the Xiphosura are by 

 Mr. Lister ; and those on the Insect a and the Arachnida 

 by Mr. Shipley. 



Our thanks are especially due to Professor Herdman, Mr. 

 Punnett, Dr. Bather, Professor MacBride, Mr. Sinclair, Dr. 

 Caiman, Mr. L. A. Borradaile, Mr. David Sharp, Mr. Hugh 

 Scott, Professor Imms, Mr. C. Warburton and Mr. C. C. 

 Dobell for reading the proofs and for the advice and assist- 

 ance which they have given in different parts of the volume. 

 Our thanks are further due to those authors and pub- 

 lishers who have allowed us to use illustrations which have 



