I40 THE ASCENT OF MAN 



This arrest of physical development at a specific 

 point is not confined to Man. Everywhere in the 

 organic world science is confronted with arrested 

 types. While endless groups of plant and animal 

 forms have advanced during the geological ages, 

 other whole groups have apparently stood still — 

 stood still, that is to say, not in time but in 

 organization. If Nature is full of moving things, 

 it is also full of fixtures. Thirty-one years ago 

 Mr. Huxley devoted the anniversary Address of 

 the Geological Society to a consideration of what 

 he called " Persistent Types of Life," and threw 

 down to Evolutionists a puzzle which has never 

 yet been fully solved. While some forms attained 

 their climacteric tens of thousands of years ago 

 and perished, others persevered, and, without ad- 

 vancing in any material respect, are alive to this 

 day. Among the most ancient Carboniferous plants, 

 for instance, are found certain forms generically 

 identical with those now living. The cone of the 

 existing Araucaria is scarcely to be distinguished 

 from that of an Oolite form. The Tabulate Corals 

 of the Silurian period are similar to those which 

 exist to-day. The Lamp-shells of our present seas 

 so abounded at the same ancient date as to give 

 their name to one of the great groups of Silurian 

 rocks — the Lingula Flags. Star-fishes and Sea- 



