CONGRUITY OF THE EVIDENCE 311 



opinions expressed by such leading evolutionists as Darwin, Herbert 

 Spencer, and Huxley. It is based upon the fact that the fauna of 

 the Cambrian age includes fossil remains of five out of the six 

 animal sub-kingdoms, namely, the Protozoa, Coelenterata, Annu- 

 loida, Annulosa, and Mollusca — representatives in fact of all the 

 sub-kingdoms save the Vertebrata, which, in the form of fishes, 

 first appear in the Silurian strata. 



Taking the data made use of by Poulton, the time he thought 

 needful to demand amounted, as Sir Edward Fry has shown in an 

 interesting article on "The Age of the Inhabited World and the 

 pace of Organic Change," to no less an astounding total than 2,700 

 million years. On the basis of 100 million years from the Cambrian 

 rocks onwards, however, the sum would still work out to 600 

 million years as the biological estimate for the duration of life 

 upon the globe.' 



As I have said, the first announcement of Lord Kelvin's con- 

 clusions undoubtedly came as a shock to biologists and geologists 

 alike. Thus Darwin, writing to Wallace on April 14, 1869, said : 

 " Thomson's views of the recent age of the world have been for 

 some time one of my sorest troubles." For even the widest limit 

 that Lord Kelvin at that time was prepared to concede for the 

 whole age of the world was altogether at variance with what would 

 be required for the mere duration of life upon its surface, in accord- 

 ance with Darwin's views as to the very slow means by which new 

 species had been evolved, and his supposition of a single starting- 

 point for living matter at some one particular time, and in some 

 one particular place on the surface of the earth. ^ 



Another of the principal reasons that made it necessary for 

 Darwin to make extremely large demands upon time is to be found 

 in his view that low forms of life change, or become modified, less 

 quickly than the higher forms.3 This same doctrine was also most 

 strongly enforced by Poulton in the before-mentioned address. He 

 said : ♦ " Undoubtedly a study of all the available evidence points 

 very strongly to the conclusion that in the lower grade, sub-grades, 

 and phyla of the animal kingdom, evolution has been extremely 

 slow as compared with that in the higher." 



But these views as to the rate of change in lower organisms are 

 based upon the most questionable data. It is obvious that Poulton 



' " Monthly Review," December, igo2, and January, 1903. 



» " Origin of Species," sixth ed., p. 429. 



3 Loc. cit, p. 346. ■• Loc. cit., p. S06. 



