:M; LIFE OF 



speaks the truth. The green and budding twigs may 

 represent existing species ; and those produced during 

 each former year may represent the long succession of 

 extinct species. At each period of growth all the growing 

 twigs have tried to branch out on all sides, and to overtop 

 and kill the surrounding twigs and branches, in the same 

 manner as species and groups of species have tried to 

 overmaster other species in the great battle for life. The 

 limbs divided into great branches, and these into lesser 

 and lesser branches, were themselves once, when the tree 

 was small, budding twigs ; and this connexion of the 

 former and present buds by ramifying branches may well 

 represent the classification of all extinct and living species 

 in groups subordinate to groups. Of the many twigs 

 which flourished when the tree was a mere bush, only two 

 or three, now grown into great branches, yet survive and 

 bearall the other branches ; so with the species which lived 

 during long-past geological periods, very few now have 

 living and modified descendants. From the first growth 

 of the tree many a limb and branch has decayed and 

 dropped off; and these lost branches of various sizes 

 may represent those whole orders, families, and genera 

 which have now no living representatives, and which 

 are known to us only from having been found 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 favoured and is still 

 alive on its summit, so we occasionally see an animal 

 like the Ornithorhynchus or Lepidosiren, which in some 

 small degree connects by its affinities two large branches 

 of life, and which has apparently been saved from 



