150 THE VIVARIUM. 
colour of the object upon which it is resting. It does so, indeed, 
sometimes ; but more by accident than by intention. Nor can it 
conceal its feelings; for example, no sooner does it experience 
fear than it proclaims that emotion by a change in the colouring 
of its body. 
Several explanations have been given in regard to the Chame- 
leon’s great power of changing colour; while some authorities 
have declared that this phenomenon is entirely inexplicable. It 
is, however, probably chiefly due to layers of pigment-cells placed 
deeply in the skin, and which are acted upon partly by the air 
which fills the lungs, and partly by two sets of ‘ nerve-fibres,”’ 
one set of which, the constrictors, withdraws the cells from near 
the surface of the skin ; while the other set, the dilators, presses 
them forward towards the skin’s surface. These nerves are more 
or less governed by the brain of the animal. 
The eyes of the Chameleon are in their way as extraordinary 
as the animal’s power of changing colour. ‘‘ One eye is able to 
look north and the other to look south,”’ as a friend one day 
quaintly put it while looking at my Reptiles ; or as the French 
say, ‘“‘ it can look into Champagne and see Picardy in flames.” 
The eye-ball is very large and prominent, and is covered with a 
single eyelid, which is pierced in the centre for the pupil. This 
opening is about as large as the head of a common pin. When 
the animal sleeps, it closes this aperture tiansversely. 
The eyes give the Chameleon the power of looking in nearly 
every direction without bending its stiff neck or altering the 
position of its body in the slightest degree. One eye, for in- 
stance, may be looking at the observer, while the other is watch- 
ing the movements of a fly in a different quarter. But both eyes 
are invariably fixed upon the insect which the Reptile is on the 
point of capturing. In pictures, one sometimes sees Chameleons 
represented as looking in one direction, while the tongue is being 
thrown forward at a fly in another. If the Chameleon ever does 
act so injudiciously as this, he will surely make a bad shot with 
his tongue. 
When it is necessary to speak of the tongue of this strange 
creature, there is a temptation to say that it 1s even more extra- 
ordinary than its eyes. The Chameleon is the only Lizard which 
