METHODS OF PROTECTION AMONG ANIMALS. 157 
Snakes present three main structures of a protective 
kind—scales developed on the integument, with which 
one must remember their remarkable power of frequently 
changing their skin, protective coloration, and among 
venomous snakes the potson-fang and gland with the mus- 
cular apparatus for ejecting a stream of the venom along 
the grooved fang placed in the front of the upper jaw. 
Time will not allow of any details being given. With these 
protective arrangements and their power of rapid sinuous 
movement snakes are not less equipped for the struggle of 
their life than other animals. The reserve fully developed 
poison-fang behind the one in use needs to be remembered. 
Indeed, it has been noticed that, considering the fact that 
non-venomous and venomous snakes get on equally well in 
life, the latter may be called over-equipped animals. The 
eyes of the snakes are provided with a thin transparent layer 
of skin for protection of these delicate organs, and this layer is 
shed with the rest of the skin and renewed. 
Lizards, inhabiting mainly the land,some the trees,andsome 
the water, are a large group of animais protected mainly by 
their colouring, active movements, and scaly skin. A few have 
a poisonous bite, but most of them are harmless. The most 
interesting from the present point of view are the chameleons, 
very sluggish, harmless creatures, mostly arboreal, but remark- 
ably protected by their power of changing colour, not only 
according to their surroundings, but from yellow at night to 
dark green at dawn, and brighter in colour as the daylight 
increases. They have a singular thin tongue, several inches 
long, which can be protruded with lghtning-lke speed to 
any ; small prey, which the sticky bulbous end captures with 
unerring skill, while the creature itself may be solemnly 
seated on a bough apparently as motionless as the bough 
itself, with only its elobuiar eye revolving in a weird manner. 
Lyddeker points out how utterly defeneciess are these 
creatures apart from these characters mentioned. 
- Among birds the structyres concerned in their protection 
are very remarkable and differ much from those of any 
other class of animals. The most characteristic are feathers ; 
epidermal structures ‘analogous to the scales of fishes and 
reptiles, or to the hair of mammalia. It is clear that there 
are two important purposes in clothing a bird with feathers. 
On the one hand, feathers are valuable non-conductors 
with the important effect.of maintaining the temperature 
of the bird’s blood in its rapid flight through cold air. 
