I’REFACK. 
vn 
four only are described in Johnston, — the rest of his species being 
either sjmonyms or resting on insufficient evidence. Fifty -four 
British species have been examined by myself, perhaps a larger 
mimber than have come under the notice of any other naturalist ; 
by far the greater part in life and health ; and thirty-foxir of 
these have been added to the British Fauna bj' myself. 
A new feature in works of this sort, which will strike the 
student, perhaps needs a word of explanation ; — I mean the dis- 
tingui.shing of the prominent varieties of each species by a 
diagnosis, and the assigning of a trivial name to each. Consider- 
ing the variability of many of the forms, I trust the convenience 
of this procedure will excuse the innovation. 
The analytical tables of the families, genera, and species, 
hitherto scarcely known in English zoological works, will, I 
think, be found useful ; nor will the attempt to tabulate the 
geographical distribution of the species be devoid of interest to 
the philosophic student. 
The plates must speak for themselves : they have been printed 
in colours by Mr. W. Dickes, who has spared no effort to make 
them, as nearly as possible, fac-similes of my original drawings, 
which were made from the life. 
Nearly two years have been occupied in the progressive publi- 
cation of the work, as it has been issued in bi-monthly parts. 
Advantages and disadvantages attend this mode of publication. 
Among the former may be reckoned that the information is 
brought down to the latest period, and that the successive parts 
stimulate the zeal and co-operation of fellow-labourers ; the book 
thus embodjdng the knowledge of many, rather than of one. 
Among disadvantages must be put doxvn, incongruities between 
the earlier and the later portions, statements made and opinions 
hazarded which are subsequently corrected, and omissions which 
are finally supplied. For these defects the author must cast 
himself on the kind consideration of his readers, who must be 
aware that no branch of science is at one stay even for a single 
month. 
