BIRDS 169 
The older pupils will be able not only to understand these 
differences, most of which should not be beyond the comprehension 
of any but the youngest children, but to appreciate the points of 
similarity between the three classes of animals. 
The description given of the Common Lizard will apply with a 
few slight modifications to other forms. These when possible 
should be obtained and examined. The common lizard is easily 
procured and moreover can he kept in confinement sufficiently 
long to enable many of its habits to be observed. 
New Zealand fortunately is almost free from reptilian life, 
so that any study of these animals beyond what is indicated 
in this chapter will have to be made by means of preserved 
specimens or pictures. 
XII.—BIRDS. 
INTRODUCTION.—Broadly speaking this class of vertebrates. 
may be distinguished from the others by possessing a covering of 
feathers. All living birds are divided into two main orders: (1) 
those having a breast-bone provided with a keel ; and (2) those 
having a flat breast-bone. ‘To the former belong all birds capable 
of flight, and to the latter those unable to fly. 
It is well in beginning the study of any class of animals, to 
select some particular form as a type and examine it closely. 
When this has been done other members of the class can be 
studied ; and by comparing and contrasting the special charac- 
teristics of the different types much useful and _ interesting 
information may be obtained. A suitable type to begin on, and 
moreover one which is easily procured, is the Common Fowl. 
The Common Fowl. The Common Fowl belongs to 
the order whose breast-bones are furnished with keels ; it 
is, therefore, a flyer. 
General Description. The body is ovoid in shape, 
tapering, in the living animal, gradually towards the head 
and tail. The fore-limbs, which in the other forms we 
have been studying served the purpose of fins or feet, are 
modified to form wings. These are set above the centre of 
