CONGRUITY OF THE EVIDENCE 313 



of the earth, we may see, not only how many of the facts con- 

 cerning " persistent types " may be explained, but also how the 

 time needed for the whole evolution of life upon the globe may 

 have been far less prolonged than biologists have hitherto supposed. 

 The naturaUst would be no longer bound to look upon all animals 

 and plants as members of a single imperfect series. The routes 

 that have given rise to all the known forms of life may have been 

 many, and several of the evolutional series may have been develop- 

 ing not only contemporaneously, but also to some extent similarly 

 from new starting points in successive geological epochs. May 

 not the existence of Amphioxus at the present day in our seas be 

 an evidence of this ? Are we to suppose that this minute organism 

 which is regarded as " the ancestral form of all vertebrates," 

 has come down to us unchanged from pre-Silurian epochs? 

 Cope iloc. cit., p. 99) speaks of a fish of the Carboniferous age as of 

 a type from which all fishes may have sprung, " although the genus 

 as now known has not sufficient antiquity to claim this place." 

 But when he adds, " It may b^ a near descendant of the 

 Amphioxus," he clearly indicates his belief in the amazing per- 

 sistence of this form of life. But who is to say that it has 

 not originated from some annelid or some tunicate during a 

 comparatively recent epoch ? A similar questionable persistence 

 is postulated by Poulton for Peripatus — though this organism 

 has also never been found in the fossil state. , 



The foregoing brief survey should suffice to show the reader 

 how much better multitudes of well-known facts can now be 

 explained, and how absolutely irreconcilable many of them are 

 with the old point of view. We have seen that this holds good in 

 reference to the following classes of facts : — 



(i) Concerning the present day existence of multitudes of the 

 lowest organisms. 



(2) Concerning their wide-spread distribution over the surface 

 of the earth. 



(3) Concerning abrupt variations (' mutations ') in higher plants 

 and animals. 



(4) Concerning the geographical distribution of higher plants 

 and animals. 



(5) Concerning the distribution of the fossil remains of higher 

 animals through the crust of the earth. 



(6) Concerning the existence of recurring or so-called " persistent 

 types " of life. 



