SOME SPECIFIC CHARACTERS 129 



regions of the earth life is ten or twenty times more 

 exuberant than with us, then the immensity of the living 

 population of the land and water of the globe becomes 

 as difficult to realize as are the figures in which the 

 astronomer tells of the number and distances of the stars. 

 On the other hand, some idea of the number of distinct 

 species of animals and plants which have up to this date 

 been recognized and described by naturalists as at present 

 existing, may be formed by a statement of those which 

 have been described in some of the more familiar groups. 

 About 10,000 species of mammals have been described ; 

 about 14,000 of birds ; 7000 of reptiles ; 15,000 of fishes ; 

 500,000 of six-legged insects ; 14,000 of Crustacea (shrimps, 

 lobsters, crabs); 62,000 of molluscs (snails, mussels, etc.); 

 15,000 of star-fishes and sea-urchins; 5000 of corals and 

 polyps ; 3000 of sponges ; and 6000 of microscopic pro- 

 tozoa. In all about 800,000 species of animals have been 

 recorded, and probably as many more remain yet to be 

 recognized and described. 



The total number of described species of plants has 

 never been estimated, but some idea of it may be formed 

 from the fact that 1860 species of flowering plants alone 

 have been distinguished in Britain, 17,000 in British India, 

 and 22,000 in Brazil, not to mention those of Africa and 

 Australia ! These figures do not include the vast numbers 

 of flowerless plants, the ferns, mosses, sea-weeds, mush- 

 rooms, moulds, lichens, and microscopic plants. 



And then we have to add to these enumerations of 

 living species the extinct species of successive geological 

 ages, the remains of which are sufficiently well preserved 

 to admit of identification. Those which are known are 

 only a few thousands in number, and a mere fragment of 

 the vast series of species which have existed in successive 

 past ages of the earth. They are a few samples of the pre- 

 decessors of the existing species, and some of them were 

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