168 NEW ZEALAND NATURE-STUDY BOOK 
tail. The male forms have larger crests than the female. 
The limbs are thick and strong and end in five toes. 
Opportunities for examining the Tuatara must neces- 
sarily be limited, the description of the animal has, 
therefore, been made as brief as possible. 
Fig. 109.— Tuatara. 
Norr.—The difference between reptiles and amphibians should 
be brought out during the course of the lessons. These dis- 
tinguishing characteristics wili not at first appear obvious to 
children, and for this reason in many of the text books on object- 
lessons the Frog is described as a reptile. Just as amphibians are 
distinguishable from fishes mainly in the structure of the limbs, 
in the absence of fins bearing fin-rays, and in the manner of 
respiration ; so reptiles differ from amphibians in the method of 
breathing and in the manner of development. The Frog obtains a 
supply of oxygen by means of lungs and through a moist skin; a 
reptile breathes by lungs only. Again the Frog passes through a 
course of development known as a metamorphosis, during which 
it obtains the necessary oxygen through an arrangement of gills ; 
the reptile is developed from an egg, is born with lungs, and is 
furnished with gills at no period of its life. 
