PREFACE TO THE FIRST EDITION 



This book is intended for the use of students who have completed 

 a year's study of the principles of zoology and of the anatomy and 

 physiology of a series of invertebrate types such as is provided by any 

 of several elementary textbooks in use in this country. The types 

 commonly included in these books — various Protozoa, Hydra , Ascaris^ 

 and the Liver Fluke, Earthworm, Leech, Crayfish, Cockroach, Pond 

 Mussel, and Starfish — are not here described in detail. We have 

 endeavoured to provide the student with a classification of the 

 Invertebrata which proceeds as far as is usual in an honours course, 

 with a concise statement of the characteristic features of each of the 

 groups mentioned, and with a more detailed statement and discussion 

 of matters of importance or interest concerning them. The choice of 

 examples has been difficult, and we have not always been able to 

 include all those we should have wished, but a fairly full account of 

 certain representative genera has been given. 



The writing of the book has been shared among us as follows: 

 Chapters I-IV, X, XI (except Onychophora), XII, XVIII and XIX 

 have been written by L. A. Borradaile, Chapters V (except Cteno- 

 phora), VII-IX, XIII, XV-XVII, and the Onychophora in Chapter 

 XI by F. A. Potts, Chapter VI and the Ctenophora in Chapter V by 

 J. T. Saunders, and Chapter XIV jointly by F. A. Potts and L. E. S. 

 Eastham, but each of us has read and criticized the work of the others. 



We desire to express our grateful thanks for valuable advice and 

 criticism to Dr S. J. Hickson, Professor D. Keilin and Dr S. M. 

 Manton; for much care bestowed upon the illustrations to Messrs 

 A. P. Hayle, J. F. Henderson, and C. F. Pond; and for valuable 

 assistance in the preparation of the index and in other matters to 

 Mr B. Newman. 



For permission to reproduce illustrations acknowledgment is due 

 to Professor G. H. F. Nuttall; Messrs Geo. Allen & Unwin, Ltd. 

 (Textbook of Zoology, Sedgwick) ; Messrs A. & C. Black, Ltd. (Treatise 

 on Zoology, Lankester); the Council of the Cambridge Philosophical 

 Society (Biological Reviews); Cambridge University Press (The De- 

 termination of Sex, Doncaster, Plant Biology, Godwin, Ciliary Move- 

 ment, Gray, Zoology, Shipley and MacBride, Primitive Animals, 

 Smith, Palceontology , Wood); Herrn Gustav Fischer, Jena (Ergebnisse 

 u. Fortschritte der Zoologie, Lehrbuch der Protozoenkunde) ; Herren 

 Walter de Gruyter & Co. (Handbuch der Zoologie) ; the Council of the 

 Linnean Society of London (Zoological Journal) ; Messrs Macmillan 

 & Co., Ltd. (Cambridge Natural History , Harmer and Shipley, Human 



