176 bELECTION. Chap. XX 



CHAPTER XX. 



SELECTION' BY MAN. 



SELECTION A DIFFICULT ART — METHODICAL. UNCONSCIOUS, AND NATURAL 

 SELECTION — RESULTS OF METHODICAL SELECTION CARE TAKEN IN SE- 

 LECTION — SELECTION "WITH PLANTS — SELECTION CARRIED ON BY THE 

 ANCIENTS AND BY SEMI-CIVILISED PEOPLE — UNIMPORTANT CHARACTERS 

 OFTEN ATTENDED TO — UNCONSCIOUS SELECTION — AS CIRCUMSTANCES 

 SLOWLY CHANGE, SO HAVE OUR DOMESTICATED ANIMALS CHANGED 

 THROUGH THE ACTION OF UNCONSCIOUS SELECTION — INFLUENCE OF 

 DIFFERENT BREEDERS ON THE SAME SUB-VARD2TY — PLANTS AS AFFECTED 

 BY UNCONSCIOUS SELECTION — EFFECTS OF SELECTION AS SHOWN BY THE 

 GREAT AMOUNT OF DIFFERENCE IN THE PARTS MOST VALUED BY MAN. 



The power of Selection, whether exercised by man, or brought 

 into play under nature through the struggle for existence and 

 the consequent survival of the fittest, absolutely depends on 

 the variability of organic beings. Without variability 

 nothing can be effected; slight individual differences, how- 

 ever, suffice for the work, and are probably the chief or sole 

 means in the production of new species. Hence our dis- 

 cussion on the causes and laws of variability ought in strict 

 order to have preceded the present subject, as well as inheri- 

 tance, crossing, &c. : but practically the present arrange- 

 ment has been found the most convenient. Man does not 

 attempt to cause variability ; though he unintentionally effects 

 this by exposing organisms to new conditions of life, and by 

 crossing breeds already formed. But variability being granted, 

 he works wonders. Unless some degree of selection be exer- 

 cised, the free commingling of the individuals of the same 

 variety soon obliterates, as we have previously seen, the 

 slight differences which arise, and gives uniformity of cha- 

 racter to the whole body of individuals. In separated 

 districts, long-continued exposure to different conditions of 

 life may produce new races without the aid of selection ; but 

 to this subject of the direct action of the conditions of life 

 I shall recur in a future chapter. 



