436 THE NATURAL HISTORY [chap, xxxix. 



complete absence of all other terrestrial forms. In birds 

 it is less striking, although still very clear, for all the re- 

 markable old-world forms which are absent from the one 

 are equally so from the other, such as Pheasants, Grouse, 

 Vultures, and Woodpeckers ; while Cockatoos, Broad-tailed 

 Parrots, Podargi, and the great families of the Honey- 

 suckers and Brush-turkeys, with many others, comprising 

 no less than twenty-four genera of land-birds, are common 

 to both countries, and are entirely confined to them. 



When we consider the wonderful dissimilarity of the 

 twff regions in all those physical conditions which were 

 once supposed to determine the forms of life — Australia, 

 with its open plains, stony deserts, dried up rivers, and 

 changeable temperate climate; New Guinea, with its 

 luxuriant forests, uniformly hot, moist, and evergreen — 

 this great similarity in their productions is almost astound- 

 ing, and unmistakeably points to a common origin. The 

 resemblance is not nearly so strongly marked in insects, the 

 reason obviously being, that this class of animals are much 

 more immediately depf^ndent on vegetation and climate 

 than are the more highly organized birds and Mammalia. 

 Insects also have far more effective means of distribution, 

 and have spread widely into every district favourable to 

 their development and increase. The giant Ornithopterse 

 have thus spread from New Guinea over the whole Archi- 

 pelago, and as far as the base of the Himalayas ; while the 



