IMMUTABILITY OF SPECIES. 



77 



there have existed different species ; but no transition 

 from those of a preceding into those of the following 



of great length, each of which is 

 characterized by different animals, 

 that the differences these animals 

 exhibit is in itself evidence of a 

 change in the species. The question 

 is, whether any changes take place 

 during one or any of these periods. 

 It is almost incredible how loosely 

 some people will argue upon this 

 point from a want of knowledge of 

 the facts, even though they seem to 

 reason logically. A distinguished 

 physicist has recently taken up this 

 subject of the immutability of species, 

 and called in question the logic of 

 those who uphold it. I will put his 

 argument into as few words as pos- 

 sible, and show, I hope, that it does 

 not touch the case. " Changes are 

 observed from one geological period 

 to another ; species which do not ex- 

 ist at an earlier period are observed 

 at a later period, while the former 

 have disappeared ; and, though each 

 species may have possessed its pecu- 

 liarities unchanged for a lapse of 

 time, the fact that, when long periods 

 are considered, all those of an earlier 

 period are replaced by new ones at a 

 later period, proves that species 

 change in the end, provided a suffici- 

 ently long period of time is granted." 

 I have nothing to object to the state- 

 ment of facts, as far as it goes, but I 

 maintain that the conclusion is not 

 logical. It is true that species are li- 

 mited to particular geological epochs; 

 and it is equally true, that, in all 

 geological formations, those of suc- 

 cessive periods are different one from 

 the other. But because they so differ, 

 does it follow that they have them- 

 selves changed, and not been ex- 

 changed for, or replaced by, others 1 

 The length of time taken for the 

 operation has nothing to do with the 

 argument. Granting myriads of years 

 for each period, no matter how many 

 or how few, the question remains 

 simply this : When the change takes 

 place,does it take place spontaneously, 



under the action of physical agents, 

 according to their law, or is it pro- 

 duced by the intervention of an agen- 

 cy not at work in that way before or 

 afterwards 1 A comparison may ex- 

 plain my view more fully. Let a 

 lover of the fine arts visit a museum 

 arranged systematically, and in which 

 the works of the different schools are 

 placed in chronological order. As he 

 passes from one room to another, he 

 beholds changes as great as those 

 which the palaeontologist observes in 

 passing from one system of rocks to 

 another. But, because these works 

 bear a closer resemblance as they 

 belong to one or the other school 

 or to periods following one another 

 closely, would the critic be in any 

 way justified in assuming that the 

 earlier works have changed into 

 those of a later period, or in denying 

 that they are the works of artists 

 living and active at the time of 

 their production 'I The question about 

 the immutability of species is iden- 

 tical with this supposed case. It is 

 not because species have lasted for 

 a longer or shorter time in past ages 

 that naturalists consider them as im- 

 mutable, but because, in the whole 

 series of geological ages, taking the 

 entire lapse of time which has passed 

 since the first introduction of ani- 

 mals or plants upon earth, not the 

 slightest evidence has yet been pro- 

 duced that species are actually trans- 

 formed one into the other. We only 

 know that they are different at dif- 

 ferent periods, as are works of art 

 of different periods and of different 

 schools ; but, as long as we have no 

 other data to reason upon than those 

 which Geology has furnished to this 

 day, it is as unphilosophical and illo- 

 gical, because such differences exist, 

 to assume that species do change, 

 and have changed, that is,are trans- 

 formed, or have been transformed, 

 as it would be to maintain that works 

 of art change in the course of time. 



