118 THE FAUNA OF 
tion of bright colouring with poisonous or noxious 
qualities is of common occurrence in animals. 
The typical tree frogs of the family Hylidae are 
widely distributed over the globe, but are absent from 
Africa south of the Sahara, from Arabia, and from 
India. They have suctorial disks at the ends of their 
toes, are usually protectively coloured in shades of 
green, the tints varying with the surroundings, and 
have glands upon the under surface whereby they can 
absorb water from the damp leaves on which they rest, 
and thus obviate the necessity for seeking ponds to 
moisten the skin. Their breeding habits are often 
peculiar. Other amphibians are not adapted for the 
arboreal life. 
In regard to fresh-water fish we may note one or two 
peculiar forms, found in the streams of the tropical 
forest, or on its seaward margin. The very peculiar 
double-breathing fishes, which are animals furnished 
both with lungs and gills, are represented in the tropical 
streams of Queensland by Ceratodus, in the tropical 
streams of Africa by Protopterus, and in those of 
South America by Lepidosiren. None of these animals 
voluntarily quit the water, but the fact that the two 
last named can breathe when buried in the mud as well 
as when swimming in water adapts them for life in 
tropical regions, where there is often a well-marked 
alternation of wet and dry seasons. 
Even more curious are the habits of the mudskippers 
(Periophthalmus), which haunt the mangrove swamps 
and mud-flats on the shores of the Indian and Pacific 
Oceans and off the coast of West Africa. These are 
bony fish which are partially adapted for life on land. 
The anterior fins are curiously modified, so that the fish 
can climb about the supporting roots of the mangroves, 
