CONGRUITY OF THE EVIDENCE 301 



such abrupt ' mutations ' are now admitted by biologists to be both 

 real and frequent — " proved up to the hilt " as an authoritative 

 writer has lately said. 



We come next to other facts relating to higher organisms, and 

 having reference not only to their distribution over the face of the 

 earth at the present day, but also to the distribution of their fossil 

 remains in the diiferent strata constituting the crust of the earth. 



The new views would seem to diminish, to an enormous extent, 

 many of the difficulties at present existing in regard to the more 

 limited geographical distribution of higher plants and animals. 

 Darwin with his usual candour said ^ : " Undoubtedly there are 

 many cases of extreme difficulty in understanding how the same 

 species could possibly have migrated from some one point to the 

 several distant and isolated points where now found." He then 

 went on to say : " Nevertheless the simplicity of the view that 

 each species was first produced within a single region captivates 

 the mind. He who rejects it, rejects the vera causa of ordinary 

 generation with subsequent migration and calls in the agency of a 

 miracle." Of course in this latter statement Darwin was referring 

 to an upholder of the obsolete view, which he so successfully 

 combated, of the supposed ' special Creation ' of species. But 

 so far from appealing to "miracle," in postulating multitudinous 

 centres of origin as possible, I appeal to the uniformity of natural 

 phenomena in space and in time. 



This last word brings us, indeed, to another and a related test for 

 the relative validity of the two views now under consideration, by 

 a comparison of the aid they may afford in tracing, what has been 

 termed, the ancestral history of organisms from a study of their fossil 

 records. It was formerly thought by geologists that rocks contain- 

 ing similar fossils were to be regarded as contemporaneous forma- 

 tions. But this view was traversed by Huxley in a celebrated 

 presidential address to the Geological Society in 1862, wherein he 

 advanced the strongest evidence in favour of the position that 

 " similarity of organic contents cannot possibly afford any proof 

 of the synchrony of the deposits which contain them ; on the 

 contrary it is demonstrably compatible with the lapse of the most 

 prodigious intervals of time, and with interposition of vast changes 

 in the organic and inorganic worlds between the epochs in which 

 such deposits were formed." And, in illustration of this lack of 

 synchrony (or identity of date) he said, " For anything that geology 

 » " Origin of Species," 6th ed., p. 320. 



