II 



ON THE TENDENCY OF VARIETIES TO DEPART INDEFINITELY 

 FROM THE ORIGINAL TYPE 



Instability of Varieties supposed to prove the permanent 

 distinctness of Species 



ONE of the strongest arguments which have been adduced 

 to prove the original and permanent distinctness of species is, 

 that varieties produced in a state of domesticity are more or 

 less unstable, and often have a tendency, if left to them- 

 selves, to return to the normal form of the parent species ; 

 and this instability is considered to be a distinctive peculi- 

 arity of all varieties, even of those occurring among wild 

 animals in a state of nature, and to constitute a provision 

 for preserving unchanged the originally created distinct 

 species. 



In the absence or scarcity of facts and observations as to 

 varieties occurring among wild animals, this argument has had 

 great weight with naturalists, and has led to a very general 

 and somewhat prejudiced belief in the stability of species. 

 Equally general, however, is the belief in what are called 

 " permanent or true varieties," races of animals which con- 

 tinually propagate their like, but which differ so slightly 

 (although constantly) from some other race, that the one is 

 considered to be a variety of the other. Which is the variety 

 and which the original species, there is generally no means 

 of determining, except in those rare cases in which the 

 one race has been known to produce an offspring unlike itself 

 and resembling the other. This, however, would seem quite 

 incompatible with the "permanent invariability of species," 



