472 THEOKY OF PROGRESSION. CHAP. XXTV. 



botanists, as before explained, that whatever may be the 

 nature of the species-making power or law, its effects are of 

 such a character as to imitate the results which variation, 

 guided by natural selection, would produce, if only we could 

 assume with certainty that there are no limits to the varia 

 bility of species. But as the anti-transmutationists are per 

 suaded that such limits do exist, they regard the hypothesis 

 as simply a provisional one, and expect that it will one day 

 be surperseded by another cognate theory, which will not 

 require us to assume the former continuousness of the 

 links which have connected the past and present states 

 of the organic world, or the outgoing with the incoming 

 species. 



In like manner, many of those who hesitate to give in 

 their full adhesion to the doctrine of progression, the other 

 twin branch of the developement theory, and who even object 

 to it, as frequently tending to retard the reception of new 

 facts supposed to militate against opinions solely founded on 

 negative evidence, are, nevertheless, agreed that on the whole 

 it is of great service in guiding our speculations. Indeed, it 

 cannot be denied that a theory which establishes a con 

 nection between the absence of all relics of vertebrata in the 

 oldest fossiliferous rocks, and the presence of man's remains in 

 the newest, which affords a more than plausible explanation of 

 the successive appearance in strata of intermediate age of the 

 fish, reptile, bird, and rnammifer, has no ordinary claims to 

 our favour as comprehending the largest number of positive 

 and negative facts gathered from all parts o*f the globe, and 

 extending over countless ages, that science has perhaps ever 

 attempted to embrace in one grand generalisation. 



But will not transmutation, if adopted, require us to 

 include the human race in the same continuous series of 

 developements, so that we must hold that man himself has 

 been derived by an unbroken line of descent from some one 



