156 NEW ZEALAND NATURE-STUDY BOOK 
dealt with, their characteristics can be emphasised and pupils 
eradually led to recognise the similarity shown by all animals 
belonging to the sub-kingdom, as well as the differences which 
determine the classes. In other words the classification should 
be incidentally learnt during the progress of the lessons. 
Differences of opinion may exist as to the best time for 
introducing some of the forms belonging to the sub-kingdoms 
described in the earlier portion of Part II. With the Vertebrate 
animals, however, the case is different; all of these likely 
to be examined will furnish suitable material for investigation 
in any department of the school. Most of the animals are 
well known and can be invested with interest both for young 
children, as well as for those in the higher classes. - 
In dealing with the fish, some familiar form should be selected, 
e.g. the Schnapper, Kahawai, or Mullet. The description given in 
the preceding pages will apply to any of the kinds most easily 
procured. The study of this class of Vertebrates should extend 
over several lessons, and during its progress a number of 
individuals should be examined. It will be necessary to procure 
both dead and living specimens, the latter can be shown in large 
glass vessels, when the manner of swimming, the use of the fins 
and the method of passing water over the gills, may be learnt by 
observation. 
When dealing with the bony framework, it may be difficult to 
obtain a complete skeleton, but this, although highly desirable if 
it can be procured, is hardly necessary for the purpose in view. 
A few typical vertebre, with the head carrying teeth and 
surrounded with bony plates, will be quite sufficient for the 
purposes of illustration. This part of the subject, however, should 
not be dealt with in the initial stages of the course. 
ff 
/ 
/ X.—THE FROG. 
\h. frog belongs to a class of vertebrate animals known 
as amphibians, which differ from fishes mainly in the 
structure of the limbs, in the absence of fins bearing fin- 
rays, and in the manner of respiration. 
