102 CONCLUDING KEMAEKS. Chap. XX VIII. 



analogous conditions, would, on an average, vary to the same 

 degree. Few men at the present day will maintain that 

 animals and plants were created with a tendency to vary, 

 which long remained dormant, in order that fanciers in after 

 ages might rear, for instance, curious breeds of the fowl, 

 pigeon, or canary-bird. 



From several causes it is difficult to judge of the amount 

 of modification which our domestic productions have under- 

 gone. In some cases the primitive parent-stock has become 

 extinct ; or it cannot be recognised with certainty, owing to 

 its supposed descendants having been so much modified. In 

 other cases two or more closely-allied forms, after being 

 domesticated, have crossed ; and then it is difficult to estimate 

 how much of the character of the present descendants ought 

 to be attributed to variation, and how much to the influence 

 of the several parent-stocks. But the degree to which our 

 domesticated breeds have been modified by the crossing of 

 distinct sjDecies has probably been much exaggerated by some 

 authors. A few individuals of one form would seldom per- 

 manently affect another form existing in greater numbers ; 

 for, without careful selection, the stain of the foreign blood 

 would soon be obliterated, and during early and barbarous 

 times, when our animals were first domesticated, such care 

 would seldom have been taken. 



There is good reason to believe in the case of the dog, ox, 

 pig, and of some other animals, that several of our races are 

 descended from distinct wild prototypes ; nevertheless the 

 belief in the multiple origin of our domesticated animals has 

 been extended by some few naturalists and by many breeders 

 to an unauthorised extent. Breeders refuse to look at the 

 whole subject under a single point of view ; I have heard 

 it said by a man, who maintained that our fowls were de- 

 scended from at least half-a-dozen aboriginal species, that the 

 evidence of the common origin of pigeons, ducks and rabbits, 

 was of no avail with respect to fowls. Bieeders overlook 

 the improbability of many species having been domesticated 

 at an early and barbarous period. They do not consider the 

 improbability of species having existed in a state of nature 

 which, if they resembled our present domestic breeds, would 



