Ill 



ORGANISMS AND THEIR ORIGIN 



The Variety of Living Creatures. — The earth has 

 come to be tenanted by practically countless hosts 

 of living creatures, whose ranks are continually 

 being thinned, and continually being recruited. 

 There are legions upon legions of species, that 

 is to say, different kinds of living creatures — 

 groups of individualities, worthy of a specific 

 name, because they differ more from the nearest 

 group than brothers or cousins differ from one an- 

 other, and because they breed true with their own 

 kind. \Miat a motley assemblage it is! There 

 are plants so minute, e. g., the Bacteria, that many 

 can hang on the point of a needle; there are the 

 hyssops on the wall and the cedars of Lebanon. 

 There are animals so minute, e. g., the Trypano- 

 some of Sleeping Sickness, that we require our best 

 microscope to see them, and there are the gigantic 

 Saurians of by-gone ages, and the still surviving 

 giants like the elephants and the giraffes and the 

 great whales. The simplest organisms are single 

 cells — invisible units of living matter; the more 

 complex are vast cities of cells with millions of 

 component units. What variety of habitat there 

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