Vi PREFACE. 
‘I'he mere bulk of the present volume is far from adequately represent- 
ing the amount of labour and anxiety which has been expended on its 
production, especially as, excepting some special artistic assistance from 
my daughter with certain of the more difficult coloured figures, I have had, 
as before, to depend solely on my own hand for the preparation of the 
text, and the index thereto, as well as for the one hundred and twenty 
nature coloured paintings illustrating the chief variations of the different 
species, in addition to which I have also prepared upwards of three 
hundred anatomical and other drawings from which the explanatory 
figures in the text have been engraved. 
Although six years have been occupied in the publication of the volume, 
this lengthy period has been very fully employed in securing and painting 
from life many of the illustrations, and in the appropriate arrangement 
and co-ordination of the mass of information accumulated during the 
past quarter of a century. 
Though it might appear almost invidious to allude to the help rendered 
by particular individuals, when so many have contributed by their observa- 
tions and aid to enhance the value and importance of the Monograph, yet 
I trust I may without injustice again recall with grateful acknowledgment 
the ever-willing and priceless help so unselfishly rendered me by my late 
dear friend Mr. CHartes AsHrorp, of Christchurch, whose matchless 
anatomical skill and scientific acumen were so pre-eminent, while the 
accuracy and beauty of his preparations and sketches is evidenced by 
the anatomical diagrams in the present work, many of which are from his 
hand, and it is to me a matter of sincere regret that my valued friend 
did not live to see the results of his long and disinterested labours placed 
permanently on record. 
To Mr. W. Dentson Roesuok, F.L.S., of Leeds, who initiated the modern 
study of slugs in the British Isles, | have also been placed under deep 
obligations for placing his extensive knowledge on the subject so freely 
at my disposal, as well as for his willing aid in any direction in which 
the work most severely pressed, and it 1s with gratitude I acknowledge 
his great and varied help. 
Mr. R. Wetcu, M.R.L.A., of Belfast, has also on very many occasions 
rendered me numerous special and valuable services, not only by furnish- 
