THE ANIMAL WORLD OF BRAZIL 



teristic of Nature ; uniformity that of civilization. In our cities there 

 are few birds beyond rooks, thrushes, blackbirds, and sparrows ; the 

 wild animals are replaced by domestic species; and even the races 

 mingle and become more uniform, just as European customs and 

 clothing are progressively spreading all over the world. 



It is easy to see that in the tropics the transmutation of forms 

 must proceed more rapidly than in temperate regions. We know that 

 procreation proceeds more rapidly in a warmer climate. Even 

 human beings reach puberty earlier in hot countries than in Europe ; 

 girls become nubile at the age of twelve. It is the same with animals, 

 and in this respect Hesse has collected a number of observed cases. 

 In Africa it has been found that a half-grown Kudu antelope is 

 fertile, and in New Zealand the imported red deer become sexually 

 mature a year earlier than in Europe. In Europe the group of 

 coleoptera known as the Asparagus Beetles needs a year for its 

 development from the egg to the perfect insect; but in Java it 

 requires only 30-31 days. The East Asiatic butterfly, Danais chrys- 

 ippus, produces one generation yearly in the northern parts of its 

 habitat ; in the southern parts it requires only 23 days for the com- 

 plete cycle, and generation follows generation. Hesse calculates that 

 an insect which lays 100 eggs could multiply, with a 30-day cycle, 

 to the extent of 488 trillions in a year, while in Europe, with two 

 generations yearly, it would produce only 5,000 offspring. 



Such an intense spate of life must necessarily result in a trans- 

 mutation of forms. The more profusely a fauna multiplies, the more 

 subtly can it adapt itself to the existing conditions of life, exploiting 

 every spot of the earth's surface. But for this new adaptations of the 

 body and the instincts are requisite. And the more prolific develop- 

 ment of the flora favoured by the torrid zone must equally enrich 

 the fauna, since every plant has one or more forms of animal life 

 dependent on it, feeding upon it or exploiting it as a dwelling-place. 

 When we climb into the mountains we find that we are leaving behind 

 us, with every plant that cannot thrive in the higher altitudes, certain 

 forms of animal life. 



Despite the thoroughly individual development of the fauna and 

 flora of South America, we must realize that its plants and animals 

 have not evolved in absolute isolation from those of the other 

 continents. To begin with, we must not forget that the ocean itself 

 is not an absolute obstacle to the distribution even of terrestrial forms 



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