ORIGIN OF SPECIES 205 



The older geologists fully recognized the magnitude 

 and importance of the great continental and other 

 changes suffered by the earth — cataclysmic, cata- 

 strophic, in character, as they described them. But 

 after Darwin's book created its great furore and 

 (championed by Fritz Mueller, and Haeckel — 

 Haeckel foremost, with his fiery enthusiasm and his 

 "life-tree" — and Huxley and Weismann) gained 

 general recognition and wide acceptance for the 

 theory of descent, including man's descent, the 

 geologists showed a tendency to minimize or ignore 

 the greatness of the several successive periods in the 

 earth's history that over wide areas were destructive 

 and inhibitive to land-life, the intervals that were 

 followed by the comparatively sudden appearance 

 of higher and ever more varied life-forms. 



Of late these periods of convulsions have been re- 

 ceiving due attention, at least by some authorities. 

 The vicissitudes suffered by the earth are vividly set 

 forth by Pirsson and Schuchert^^ and by Suess.^^ 



Of course, the fact that geology has not disclosed 

 a complete life-series, is only a negative difficulty. 

 All who hold the theory of descent believe that a 

 complete geologic record would disclose an unbroken 

 line of descent. . 



11 A Text-Bool: of Geology, 450. 



12 The Face of the Earth, I. 



