CHAP. XXVI.] THE RATE OF VARIATION. 343 



ing a variety with smooth fruit instead of spinous.^ Here 

 are two cases of vxiriations amounting to specific differ- 

 ences, which appeared suddenly, and were propagated by 

 seed : they are in fact cases of the production of new 

 species, not by gradual, but by sudden variation, and they 

 would be recognised as such if they had appeared in the 

 wild state. The otter, or Ancon, sheep of ISTorth America Ancon 

 was also the result of a sudden variation ; and the differ- 

 ence in the form of its skeleton from that of the common 

 sheep amounted to a specific if not a generic difference. 

 Thus we see that sudden as well as gradual variation may 

 give rise to what are really new species, both of plants 

 and animals. It is true, these instances, and others tliat 

 could be mentioned,^ have arisen under domestication ; 

 but why may not the same have taken place in the 

 wild state ? Darwin thinks they do not : " Various 

 general reasons," he says, " could be assigned against such 

 a belief: for instance, without separation a single monstrous 

 variation would almost certainly be soon obliterated by 

 crossing."^ I think this difficulty is quite imaginary. We 

 know that vegetable species and varieties usually propagate 

 their kind truly ; and among animals, once a race has been 

 formed, the instinct of every race to unite with its own Instinct 

 kind will, in the wild state, prevent crossing. Besides, prevent 

 even if they unite, it is by no means certain that their crossing, 

 union would produce a mixed race, having characters Crossing 

 intermediate between the two parent stocks. When two produce°a 

 slightly different individuals unite, the offspring, no doubt, mLxedrace. 

 have on th^ average an intermediate character ; and thus 

 it is that where free intercrossing is permitted, separate 

 breeds do not usually arise in the same country. But this 

 is not always the case when the union is between indi- 

 viduals of very unlike races. "When the Ancons (or 



1 P. 197. 



2 " It is certain ttat the Ancon and Mancliamp breeds of sheep, and 

 almost certain that the niata cattle, turnspit and pug dogs, jumper and 

 frizzled fowls, short-faced tumbler pigeons, hook-billed ducks, &c. and 

 with plants a multitude of varieties, suddenly appeared in nearly the sanie 

 state as we now see them." (Darwin's Variation under Domestication, 

 vol. ii. p. 414.) ^ Ibid. 



