i62 THE ORIGIN OF LIFE 



most careful consideration. His observations will 

 no doubt give rise to a great deal of 

 controversy, and whether they are accepted as final 

 or not, there can be no question that the track 

 which he has followed is also the one on which 

 progress is before long destined to be made, for 

 there is much circumstantial evidence of the trans- 

 formation or heterogenesis of living types in the 

 remote past. We cannot imagine that types have 

 always been what they are ; although natural 

 selection has played a most conspicuous part in 

 bringing about such changes, the change from one 

 such type to another, or rather the transmutation 

 of species, is scarcely to be unexpected. 



As in the case of the chemical elements, such 

 analogous transformation was not believed in on 

 direct evidence till very recently ; indeed, not tiU 

 Sir William Eamsay and Mr. Soddy found that 

 radium emanation is converted into helium, 

 although there is much circumstantial evidence 

 that transmutations of the elements did at one 

 time occur. 



So also the transmutation or heterogenesis of species 

 is at the present day not at all unlikely, and we 

 fear that it would be the height of presumption on 

 the part of any thinker, sacred or profane, to assent 

 dogmatically that the principle which has been 

 violated, even in the case of the elements, where 

 the distinctive features seem so marked, should not 

 also have been violated in the case of the bio- 

 logical elements, if they might be so called, of 



