PREFACE, vii 



For example, the temptation to partition such time-honoured 

 institutions as the Ganoidei and some of the Orders of 

 Insects is almost irresistible. However, our whole system 

 of Zoological Classification is in such confusion that the 

 aoption of any particular scheme appears at present to be 

 purely arbitrary. 



The thanks of the publishers and myself are due to 

 Messrs A. & C. Black, Messrs Cassell & Co., and Messrs 

 Methven & Co., to whom we are indebted for the use of a 

 number of the illustrations. I have also to record my 

 indebtedness to ,my friend and assistant, Mr R. A. Staig \ 

 he has not only contributed several of the illustrations, but, 

 in addition, his lengthy experience of zoological teaching 

 in the Edinburgh Medical School has been productive of 

 some valuable hints and suggestions. To Dr Ashworth 

 I am also under an obligation for kindly reading over the 

 portion relating to the Lobworm, which is largely illustrated 

 from his original work. 



1 have also to thank Dr Traquair, F.R.S., for kind 

 permission to reproduce certain of the specimens in the 

 Edinburgh Museum of Science and Art. 



Finally, I must express my thanks to Messrs E. & S. 

 Livingstone, who have met my wishes with respect to 

 illustrations and to the general scope of the work with a 

 rare liberality. 



ARTHUR T. MASTERMAN. 



New School, 

 School of Medicine. 



