123 RECENT ADVANCES IN NATURAL SCIENCE ix 



which we see around us, and the existence of which we know 

 from their fossil remains, are the product, not of independent 

 creations, but of descent with gradual modification from pre- 

 existing forms. In short, the law of the natural descent of 

 individuals, of varieties, races, or breeds (which being within 

 the limits of the previous powers of observation, was already 

 universally admitted), has been extended to the still greater 

 modifications constituting what we call species, and con- 

 sequently to the higher groups called genera, families, and 

 orders. The barrier fancied to exist between so-called varieties 

 and so-called species has broken down. 



Any one commencing the study of the subject at the 

 present time without prejudice, and carefully investigating the 

 evidence upon which to form his conclusions, bearing in mind 

 that he must look for his proofs, not so much in direct 

 experiments or absolute demonstrations, which from the nature 

 of the case are impossible, but in the convergence of the 

 indications furnished by the interpretations of multitudinous 

 facts of most diverse kinds, must find it extremely difficult to 

 place himself in the position of those who held the older view, 

 so much more reasonable, so much more in accordance with 

 all that we know of the general phenomena of nature, does 

 this new one seem. In fact the onus probandi now appears 

 entirely to lie with those who make the assertion that species 

 have been separately created. Where, it may be asked, is the 

 shadow of a scientific proof that the first individual of any 

 species has come into being without pre-existing parents ? 

 Has any competent observer at any time witnessed such an 

 occurrence ? The apparent advent of a new species in geo- 

 logical history, a common event enough, has certainly been 

 cited as such. As well might the presence of a horse in a 

 field, with no sign of other animals of the same kind near it, 

 be quoted as evidence of the fallacy of the common view of 

 the descent of individuals. Ordinary observation tells us of 

 the numerous causes which may have isolated that horse from 

 its parents and kindred. Geologists know equally well how 

 slight the chances of more than a stray individual or fragment 

 of an individual here and there being first preserved and 

 afterwards discovered to give any indication of the existence 



