THE EVOLUTION OF MAN. 



CHAPTER XV. 

 THE DURATION OF HUMAN TRIBAL HISTORY. 



Comparison of Ontogenetic and Phylogenetic Periods of Time. Duration of 

 Germ-history in Man and in Different Animals. Extreme Brevity of 

 the Latter in Comparison with the Immeasurable Long Periods of 

 Tribal History. Relation of this Rapid Ontogenetic Modification to the 

 Slow Phylog-enetic Metamorphosis. Estimate of the Past Duration of 

 the Organic World, founded on the Relative Thickness of Sedimentary 

 Rouk-strata, or Neptunian Formations. The Five Main Divisions in 

 the Latter : I. Primordial, or Archilithic Epoch. II. Primary, or 

 Palaeolithic Epoch. HI. Secondary, or Mesolithic Epoch. IV. Tertiary, 

 or Caenolithic Epoch. V. Quaternary, or Anthropolithic Epoch. The 

 Relative Duration of the Five Epochs. The Results of Comparative 

 Philology as Explaining the Phylogeny of Species. The Inter-relations 

 of the Main Stems and Branches of the Indo-Germanic Languages are 

 Analogous to the Inter-relations of the Main Stems and Branches of 

 the Vertebrate Tribe. The Parent Forms in both Cases are Extinct. 

 The Most Important Stages among the Human Ancestral Forms. 

 Monera originated by Spontaneous Generation. Necessity of Sponta- 

 neous Generation. 



"In vain as yet has it been attempted to draw an exact line of demarcation 

 between historic and prehistoric times ; the origin of man and the period of 

 his first appearance pass back into indefinable time ; the so-called archaic 

 age cannot be sharply distinguished from the present age. This is the fate 

 of all geological, as of all historical periods. The periods which we dis- 

 tinguish are, therefore, more or less arbitrarily defined, and, like tho divisions 



