1V. PREFACE. 
in the work done, it was essential to have printed instruc- 
tions for the students ; and I have thought that by making 
these instructions rather fuller than necessary for class 
work, they may be also found useful for self-instruction. 
The microscope is to the Biologist what the telescope 
is to the Astronomer, and it is essential that the student 
should acquire some dexterity in its use before proceeding 
to the study of his more immediate subject. For this reason 
I have given, in the first part, a short description of a com- 
pound microscope, and some exercises in its use. These 
exercises are only to be considered as suggestive, they can 
be varied to any extent; but I have found that five or six 
hours practice is generally sufficient to enable the student 
to go on to the second part. 
In selecting the animals for examination, in the second 
part, | have been guided by the following considerations :— 
They should be widely distributed in New Zealand; they 
should be abundant, so that the teacher can supply plenty of 
material to each of the students; they should, as far as 
possible, be procurable at all seasons of the year; they should 
represent as many different groups as possible; and they 
should be different from those already described in Huxley 
and Martin's “Practical Biology;” for I look upon this book as 
an introduction to that far better one. I have not been equally 
successful in the treatment of each example, but I know from 
experience that no directions are given which cannot be car- 
ried out by any student with a little practice. In several 
of the exercises I have introduced diagnoses of species, and, 
