Chap. XXVIII. 



CONCLUDING REMARKS. 



415 



notof 



A'* 



habits of life, it will rarely happen that one part alone will be 

 modified ; but the co-adapted modifications, as formerly shown, 

 need not be absolutely simultaneous. Many variations, however 

 are from the first connected by the law of correlation. Hence 

 it follows that even closely-allied species rarely or never differ 

 from each other by some one character alone ; and this same 

 remark applies to a certain extent to domestic races ; for these 

 if they differ much, generally differ in many respects. 



Some naturalists boldly insist 1 that species are absolutely 

 distinct productions, never passing by intermediate links into 

 each other ; whilst they maintain that domestic varieties can 

 always be connected either with each other or with their parent- 

 forms. But if we could always find the links between the 

 several breeds of the dog, horse, cattle, sheep, pigs, &c, the 

 incessant doubts whether they are descended from one or several 

 species would not have arisen. The greyhound genus, if such a 

 term may be used, cannot be closely connected with any other 

 breed, unless, perhaps, we go back to the ancient Egyptian 

 monuments. Our English bulldog also forms a very distinct breed. 

 In all these cases crossed breeds must of course be excluded, for 

 the most distinct natural species can thus be connected. By 

 what links can the Cochin fowl be closely united with others ? 

 By searching for breeds still preserved in distant lands, and by 

 going back to historical records, tumbler-pigeons, carriers, and 

 barbs can be closely connected with the parent rock-pigeon ; 

 but we cannot thus connect the turbit or the pouter. The 

 degree of distinctness between the various domestic breeds 

 depends on the amount of modification which they have under- 

 gone, and especially on the neglect and final extinction of the 

 linking, intermediate, and less valued forms. 



It has often been argued that no light is thrown, from the ad- 

 mitted changes of domestic races, on the changes which natural 

 species are believed to undergo, as the former are said to be mere 

 temporary productions, always reverting, as soon as they become 

 feral, to their pristine form. This argument has been well com- 

 bated by Mr. Wallace; 2 and full details were given in the thir- 

 teenth chapter, showing that the tendency to reversion in feral 



1 Godron, < De l'Espece,' 1859, torn. ii. p. 44, &c. 



2 Journal Proc. Linn. Soc, 1858, vol. iii. p. 60. 



