12 DEGENERATION. 



shown that the strata of the earth's crust and its 

 mountains, rivers, and seas were due to the long- 

 continued operation of the very same general causes 

 — the physico-chemical causes — which at this mo- 

 ment are in operation and are continuing their work 

 of change, yet the living matter on the crust of 

 the earth had to be excluded from the grand 

 uniformity which was elsewhere , complete. 



The first hypothesis, then, which was present to 

 Mr. Darwin's mind, as it had been to that of other 

 earher naturalists, was this : "■ Have not all the 

 varieties or species of living things (man, of course, 

 included) been produced by the continuous operation 

 of the same set of physico-chemical causes which 

 alone we can discover, and which alone have been 

 proved sufficient to produce everything else } " "' If 

 this be so," Mr. Darwin must have argued (and here 

 it was that he boldly stepped beyond the specula- 

 tions of Lamarck and adopted the method by which 

 Lyell had triumphantly established Geology as a 

 science), " these causes must still be able to produce 

 new forms, and are doing so wherever they have 

 opportunity," He had accordingly to bring the 

 matter to the test of observation by seeking for 



