1512 THE STORY OF THE UNIVERSE 



ished when the tree was a mere bush, only two or 

 three, now grown into great branches, yet survive and 

 bear the other branches; so with the species which 

 lived during long-past geological periods, very few 

 have left living and modified descendants. From 

 the first growth of the tree, many a limb and branch 

 has decayed and dropped off; and these fallen 

 branches of various sizes may represent those whole 

 orders, families, and genera which have now no liv- 

 ing representatives, and which are known to us only 

 in a fossil state. As we here and there see a thin 

 straggling branch springing from a fork low down in 

 a tree, and which by some chance has been favored 

 and is still alive on its summit, so we occasionally 

 see an animal like the Ornithorhynchus or Lepido- 

 siren, which in some small degree connects by its 

 affinities two large branches of life, and which has 

 apparently been saved from fatal competition by 

 having inhabited a protected station. As buds give 

 rise by growth to fresh buds, and these, if vigorous, 

 branch out and overtop on all sides many a feebler 

 branch, so by generation I believe it has been with 

 the great Tree of Life, which fills with its dead and 

 broken branches the crust of the earth, and covers 

 the surface with its ever-branching and beautiful 

 ramifications. 



