CONTESTS. Vll 



VARIETY — PLANTS AS AFFECTED BY UNCONSCIOUS SELECTION — 

 EFFECTS OF SELECTION AS SHOWN BY THE GREAT AMOUNT OF 

 DIFFERENCE IN THE PARTS MOST VALUED BY MAN .. Pages 176-208 



CHAPTER XXI. 



selection, continued. 



STATURAL SELECTION AS AFFECTING DOMESTIC PRODUCTIONS — CHARAC- 

 TERS WHICH APPEAR OF TRIFLING VALUE OFTEN OF REAL IM- 

 PORTANCE — 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 ESPE- 

 CIALLY FAVOURABLE — WHEN NO SELECTION IS APPLIED, DISTINCT 

 RACES ARE NOT FORMED — HIGHLY-BRED ANIMALS LIABLE TO DE- 

 GENERATION TENDENCY IN MAN TO CARRY THE SELECTION OF 



EACH CHARACTER TO AN EXTREME POINT, LEADING TO DIVERGENCE 

 OF CHARACTER, RARELY TO CONVERGENCE CHARACTERS CON- 

 TINUING TO VARY IN THE SAME DIRECTION IN WHICH THEY HAVE 

 ALREADY VARIED — DIVERGENCE OF CHARACTER WITH THE EX- 

 TINCTION 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 209-236 



CHAPTER XXII. 



CAUSES OF VARIABILITY. 



VARIABILITY DOES NOT NECESSARILY ACCOMPANY REPRODUCTION 



CAUSES ASSIGNED BY VARIOUS AUTHORS INDIVIDUAL DIFFERENCES 



VARIABILITY OF EVERY KIND DUE TO CHANGED CONDITIONS OF 



LIFE — ON THE NATURE OF SUCH CHANGES — CLIMATE, FOOD, EX- 

 CESS OF NUTRIMENT — SLIGHT CHANGES SUFFICIENT — EFFECTS OF 

 GRAFTING ON THE VARIABILITY OF SEEDLING-TREES — DOMESTIC PRO- 

 DUCTIONS BECOME HABITUATED TO CHANGED CONDITIONS — ON THE 

 ACCUMULATIVE ACTION OF CHANGED CONDITIONS — CLOSE INTER- 

 BREEDING AND THE IMAGINATION OF THE MOTHER SUPPOSED TO 



