324 The Realm of Nature CHAP. 



emu and cassowary are allied to the ostrich family ; the 

 bower-bird, which delights in laying out the ground in front 

 of its nest like a garden ornamented with pebbles and flowers, 

 cockatoos, and the black swan, are characteristic birds. 

 Australian animals are found in all the islands of the Archi- 

 pelago northward and westward to Celebes and Lombok. 



416. Island Life. From Wallace's researches in the 

 Malay Archipelago it appears that an entirely different 

 fauna and a largely different flora live on adjacent islands 

 in identical physical conditions. Hence he concludes that 

 the islands on the Australian side of the dividing line have 

 not been united with those on the Asiatic side since the 

 fossil marsupials of the northern hemisphere were alive. 

 It is equally evident that the islands of Lombok and 

 Celebes have been connected with Australia, and that Bali 

 and Borneo have been connected with Asia by land which 

 has been submerged so recently that the organisms have 

 not yet had time to be much modified from the type 

 of their continental contemporaries. Similarity of faunae 

 between the Malay Archipelago and South America, and 

 many resemblances in the flora of the three southern conti- 

 nents, indicate the probability of a former Antarctic land 

 connection right round the world, which is not contradicted 

 by the configuration of the bed of the Southern Ocean. 

 Purely oceanic islands are usually inhabited only by species 

 which might have been conveyed by sea from the nearest 

 continent, and often contain very remarkably modified 

 forms. 



4 1 7. Action of Living Creatures on the Earth. The 

 processes of erosion by which the continents are carved 

 into their present form are largely modified by the action 

 of living creatures. Corals and other marine organisms 

 are powerful agents in rock-making ( 280). Forests, and 

 the growth of vegetation generally, bind the soil together, 

 preventing denudation on mountain slopes, reclaiming 

 alluvial terraces in rivers, and often putting a stop to the 

 drift of sand-dunes. Vegetation also affects climates, pro- 

 ducing a uniform rainfall, checking evaporation, and regu- 

 lating the flow of rivers by absorbing the water of heavy 



