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SELECTION. chap. XXI. 



functions and mutual relations of parts— will be rigorously tested, 

 preserved, or rejected. Natural selection often checks man's 

 comparatively feeble and capricious attempts at improvement ; 

 and if this were not so, the result of his work, and of nature's 

 work, would be even still more different. Nevertheless, we must 

 not overrate the amount of difference between natural species 

 and domestic races ; the most experienced naturalists have often 

 disputed whether the latter are descended from one or from 

 several aboriginal stocks, and this clearly shows that there is no 

 palpable difference between species and races. 



Domestic races propagate , their kind far more truly, and 

 endure for much longer periods, than most naturalists 

 willing to admit. Breeders feel no doubt on this head- ask 

 a man who has long reared Shorfhorn or Hereford cattle, 



ucester or Southdown sheep, Spanish or Game poultry, 

 tumbler or carrier-pigeons, whether these races may not have 

 been derived from common progenitors, and he will probably 

 laugh you to scorn. The breeder admits that he may hope to 

 produce sheep with finer or longer wool and with better carcases, 

 or handsomer fowls, or carrier-pigeons with beaks just percep- 

 tibly longer to the practised eye, and thus be successful at an 

 exhibition. Thus far he will go, but no farther. He does not 

 reflect on what follows from adding up during a long course of 



time many, slight, successive modifications : nor does he reflect 



are 



L 



le source. But ask him whether the closely allied natural 

 species which he has studied may not have descended from a 

 common progenitor, and he in his turn will perhaps reject the 

 notion with scorn. Thus the naturalist and breeder may mutually 

 learn a useful lesson from each other. 



Summary on Selection hy Man.— There can be no doubt that 



on the former existence of numerous varieties, connecting the 

 links in each divergent line of descent. He concludes, as was 

 shown in the earlier chapters, that all the chief breeds to which 

 he has long attended are aboriginal productions. The systematic 

 naturalist, on the other hand, who generally knows nothing of 

 the art of breeding, who does not pretend to know how and 

 when the several domestic races were formed, who cannot have 

 seen the intermediate gradations, for they do not now exist, 

 nevertheless feels no doubt that these races are sprung from a > 



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