Chap. XXI. NATUKAL SELECTION. 209 



CHAPTEK XXI. 



SELECTION, continued. 



NATURAL SELECTION AS AFFECTING DOMESTIC PRODLCTIONS CHARACTERS 



WHICH APPEAR OP TRIFLING VALUE OFTEN OF REAL IMPORTANCE — 



CIRCUMSTANCES FAVOURABLE TO SELECTION BY MAN FACILITY IN 



PREVENTING CROSSES, AND THE NATURE OF THE CONDITIONS — CLOSE 

 ATTENTION AND PERSEVERANCE INDISPENSABLE — THE PRODUCTION OF A 

 LARGE NUMBER OF INDIVIDUALS ESPECIALLY FAVOURABLE — WHEN NO 

 SELECTION IS APPLIED, DISTINCT RACES ARE NOT FORMED — HIGHLY-BRED 

 ANIMALS LIABLE TO DEGENERATION — TENDENCY IN BIAN TO CARRY THE 

 SELECTION OF EACH CHARACTER TO AN EXTREME POINT, LEADING TO 

 DIVERGENCE OF CHARACTER, RARELY TO CONVERGENCE — CHARACTEliS 

 CONTINUING TO VARY IN THE SAME DIRECTION IN WHICH THEY HAVE 

 ALREADY VARIED — DIVERGENCE OF CHARACTER, WITH THE EXTINCTION 

 OF INTERMEDIATE VARIETIES, LEADS TO DISTINCTNESS IN OUR DOMESTIC 

 RACES — LIMIT TO THE POWER OF SELECTION — LAPSE OF TIME IMPORTANT 

 — MANNER IN WHICH DOMESTIC RACES HAVE ORIGINATED — SUMMARY. 



Natural Selection, or tlie Survival of the Fittest, as affecting 

 domestic productions. — We know little on this head. But as 

 animals kept by savages have to provide throughout the year 

 their own food either entirely or to a large extent, it can 

 hardly be doubted that in different countries, varieties dif- 

 fering in constitution and in various characters would 

 succeed best, and so be naturally selected. Hence perhaps it 

 is that the few domesticated animals kept by savages partake, 

 as has been remarked by more than one writer, of the wild 

 appearance of their masters, and likewise resemble natural 

 species. Even in long-civilised countries, at least in the 

 wilder parts, natural selection must act on our domestic races. 

 It is obvious that varieties having very different habits, consti- 

 tution, and structure, would succeed best on mountains and 

 on rich lowland pastures. For example, the improved Lei- 

 cester sheep were formerly taken to the Lammermuir Hills ; 

 but an intelligent sheep-master reported that " our coarso 

 " lean pastures were unequal to the task of supporting such 

 " heavy-bodied sheep ; and they gradually dwindled away 

 " into less and less bulk : each generation was inferior to the 



