xvm PAST HISTORY 349 



the Old Red Sandstone was formed, there are few survivors 

 to-day. The New Zealand lizard, Sphenodon or Hatteria, 

 is the sole survivor of an ancient race, and the same may 

 be said of the king-crab (Limulus), another " living fossil." 

 It is difficult to explain why some of the old types 

 disappeared. The extinction was never sudden. For- 

 midable competitors may have helped to weed out some ; 

 for cuttlefish would tend to exterminate trilobites, and 

 voracious fishes would decimate cuttlefish, just as man 

 himself is rapidly and inexcusably annihilating many 

 kinds of beasts and birds. But, apart from the struggle 

 with competitors, it is likely that some types were in- 

 sufficiently plastic to save themselves from changes of 

 environment, and it seems likely that others were victims 

 to their own constitutions, becoming too large, or too 

 sluggish, or too calcareous ; or, on the other hand, too 

 feverishly active. The ' scouts " of evolution would be 

 apt to become martyrs to progress ; the " laggards ' 

 in the race would tend to become pillars of salt ; the path 

 of success was oftenest a via media of compromise. 

 Samuel Butler has some evidence for saving that " the 



m 



race is not in the long run to the phenomenally swift, nor 

 the battle to the phenomenally strong ; but to the good 

 average all-round organism that is alike shy of radical 

 crotchets and old- world obstructive ness." 



5. Relative Antiquity of Animals. We have not much 

 satisfaction in submitting the following table showing 

 the relative antiquity of the higher animals. Such a table 

 is only an approximation ; it does not suggest the great 

 differences in the duration of the various periods, nor how 

 the classes of animals waxed and waned, nor how some 

 types in these classes dropped off while others persisted. 

 But the general fact which the table shows is true, in 

 the course of time higher and higher forms of life have 

 come into being. It is possible to offer explanations of 

 some apparent difficulties, e.g. that the earliest known 

 mammalian fossils precede those of the earliest known 

 bird fossils, for the two classes are on quite different lines 

 of evolution ; the big fact is certain that throughout the 

 ages life has been slowly creeping upwards. 



