426 



CONCLUDING REMARKS. 



Chap. XXVIII 



production of 



varieties and 



extinction has in- 



y recurred. At the present time improved breeds 



times displace at an 



dinarily rapid rate older breeds 



The 



has recently occurred throughout England with pig 



suddenly 



ay as if by some murderous pestilence," by the introduction 



Long-horn cattle in thei 



of Short-hoi 



What grand results have followed from the long-continued 



checked and 

 q, is seen on 



action of methodical and unconscious selectio 



regulated to 



by natural selectio 



a 



r 



y side of us. Compare the many animals and plants which 

 displayed at our exhibitions witli their parent-forms when 



suit old 



to their for 



the 



historical records with respect 

 state. Almost all our domesticated animals 

 have given rise to numerous and distinct races, excepting those 

 which cannot be easily subjected to selection — g 

 cochineal insect, and the hive-bee, — and exceptm 

 which are not much valued. In accordance with what we know 

 of the process of selection, the formation of our many races has 

 been slow and gradual. The man who first observed and pre- 

 served a pigeon with its oesophagus a little enlarged, its beak a 

 little longer, or its tail a little more expanded than usual, never 

 dreamed that he had made the first step in the creation of the 





pouter, carrier, 



fantail-pi 



Man can create not only 



anomalous breeds, but others with their whole structure ad- 

 mirably co-ordinated for certain purposes, such as the race-horse 

 and dray-horse, or the greyhound. It is by no means necessary 

 that each small change of structure throughout the body, leading 

 towards excellence, should simultaneously arise and be selected. 

 Although man seldom attends to differences in organs which 

 are important under a physiological point of view, yet he has 



so profoundly modified some breeds, that 

 they would be ranked under distinct gen 



a 



edly, if found 



The best proof of 



selection has effected is perhaj 



afforded by 

 animal, and 



fact that whatever part or quality in any 



rnor 



especi 



any pi 



s most valued by 

 the several races. 



man, that part or quality differs in 

 This result is well seen by comparing 



7 Youatt on Cattle, 1834, p 200 : on Pigs, see « Gard. Chronicle/ 1854, p. 410. 



the amount of differ 



