PREFACE, vil 
For example, the temptation to partition such time-honoured 
institutions as the Ganotdei and some of the Orders of 
Insects is almost irresistible. However, our whole system 
of Zoological Classification is in such confusion that the 
adoption 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 ScHOoOoL, 
ScHOOL oF MEDICINE. 
