Poko lt AsGor, 
In bringing out a Text-book of Natural History intended 
mainly for the use of schools, there are a few remarks which 
it may be as well to make by way of preface, if only to 
explain the principles upon which the work has been 
written. 
In the first place, more space has been devoted, coms 
paratively speaking, to the Invertebrate Animals than has 
usually been the case in introductory works, upon the 
belief that any practical Zoological work likely to be under- 
taken by young students will certainly be in connection 
with these rather than with the Vertebrate Animals. 
Secondly, the Author has devoted considerable space 
to a discussion of the principles of Zoological classifica- 
tion, believing that it is of paramount importance that the 
student should have a clear idea of the principles upon 
which the Animal Kingdom has been systematically divided. 
At the same time, the introductory portion of the work is 
more especially intended for the teacher; and there is much 
in it that the learner may perhaps hardly understand till he 
has arrived at some clear idea of Natural History as a 
whole. 
Thirdly, whilst the Author trusts that the style of the 
work will be found clear and intelligible, he does not 
