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LAW OF DESCENT 95 



the entirely new science of paleontology, opening up worlds of 

 organic life before unknown, also showing infinite gradations of 

 structure, but mainly important as increasing our horizon of 

 observation to an extent not previously dreamt of in the direction 

 of time. Powers of observation formerly limited to the brief 

 space of a few generations are now extended over ages which 

 the concurrent testimony of various branches of knowledge — of 

 astronomy, cosmogony, and geology — show are immeasurable 

 compared with any periods of which we hitherto had cognisance. 

 The result may be stated to be that the opinion now almost if 

 not quite universal among skilled and thoughtful naturalists of all 

 countries, whatever their beliefs on other subjects, is that the 

 various forms of life which we see around us, and the existence 

 of which we know from their fossil remains, besides the in- 

 numerable others of which the remains do not exist or have not 

 yet been discovered, are the product not of independent creations, 

 but of descent with gradual modifications 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 are already universally admitted), has been 

 extended to the still greater modifications constituting what we 

 call species, and consequently to the higher groups called genera, 

 families, and orders. The barrier fancied to exist beween so- 

 called varieties and so-called species has broken down. In fact 

 the onus probandi now seems entirely to lie with those who make 

 the assertion that species have been separately created. Where, 

 in fact, it may be asked, is the shadow of a scientific proof that 

 the first individual of any species has come into being without 

 pre-existiing parents ? Has any competent observer at any time 

 witnessed such an occurrence ? The apparent advent of a new 

 species in geological history, a common event enough, has certainly 

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

 field with no other animals 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 are the chances of more than a stray 

 individual or fragment of an individual here and there being 



