IV 



CONTENTS OF VOL. II 



RESPONDING PERIODS OF LIFE 



THE IMPORTANCE OF THE PRINCIPLE WITH RESPECT 



TO EMBRYOLOGY ; AS EXHIBITED IN DOMESTICATED ANIMALS ; AS EXHIBITED IN 

 THE APPEARANCE AND DISAPPEARANCE OF INHERITED DISEASES ; SOMETIMES 



THAN 



SUMMARY OF THE 



THREE PRECEDING CHAPTERS 



Page 62 







CHAPTEE XV. 



ON CROSSING. 



FREE INTERCROSSING OBLITERATES THE DIFFERENCES BETWEEN ALLIED BREEDS 

 WHEN THE NUMBERS OF TWO COMMINGLING BREEDS ARE UNEQUAL, ONE ABSORBS 



— THE RATE OF ABSORPTION DETERMINED BY PREPOTENCY OF TRANS- 



THE OTHER 



MISSION, BY THE CONDITIONS OF LIFE, AND BY NATURAL SELECTION — ALL ORGANIC 

 BEINGS OCCASIONALLY INTERCROSS : APPARENT EXCEPTIONS — 



•> 



— ON CERTAIN 

 CHARACTERS INCAPABLE OF FUSION; CHIEFLY OR EXCLUSIVELY THOSE WHICH 



HAVE SUDDENLY APPEARED IN THE INDIVIDUAL — ON THE MODIFICATION OF OLD 



RACES, AND THE FORMATION OF NEW RACES, BY CROSSING 



SOME CROSSED RACES 



HAVE BRED TRUE FROM THEIR FIRST PRODUCTION 



ON THE CROSSING OF DISTINCT 



SPECIES IN RELATION TO THE FORMATION OF DOMESTIC RACES 85 



CHAPTER XYI. 



CAUSES WHICH INTERFERE WITH THE FEEE CROSSING OF 



VARIETIES 



INFLUENCE OF DOMESTICATION ON FERTILITY. 



DIFFICULTIES IN JUDGING OF THE FERTILITY OF VARIETIES WHEN CROSSED 

 VARIOUS CAUSES WHICH KEEP VARIETIES DISTINCT, AS THE PERIOD OF BREEDING 

 AND SEXUAL PREFERENCE — VARIETIES OF WHEAT SAID TO BE STERILE WHEN 



CROSSED 



— VARIETIES OF MAIZE, VERBASCUM, HOLLYHOCK, GOURDS, MELONS, AND 

 TOBACCO, RENDERED IN SOME DEGREE MUTUALLY STERILE — DOMESTICATION 

 ELIMINATES THE TENDENCY TO STERILITY NATURAL TO SPECIES WHEN CROSSED 

 ON THE INCREASED FERTILITY OF UNCROSSED ANIMALS AND PLANTS FROM 

 DOMESTICATION AND CULTIVATION 100 



> I ' 



CHAPTER XVII. 



ON THE GOOD EFFECTS OF CROSSING, AND ON THE EVIL 



EFFECTS OF CLOSE INTERBREEDING. 



DEFINITION OF CLOSE INTERBREEDING — AUGMENTATION OF MORBID TENDENCIES — 

 GENERAL EVIDENCE ON THE GOOD EFFECTS DERIVED FROM CROSSING, AND ON THE 



EFFECTS FROM CLOSE INTERBREEDING — CATTLE, CLOSELY INTERBRED ; HALF- 



EVIL 



WILD CATTLE LONG KEPT IN THE SAME PARKS — SHEEP — FALLOW-DEER — DOGS — 

 RABBITS — PIGS — MAN, ORIGIN OF HIS ABHORRENCE OF INCESTUOUS MARRIAGES 

 FOWLS — PIGEONS — HIVE-BEES — PLANTS, GENERAL CONSIDERATIONS ON THE 

 BENEFITS DERIVED FROM CROSSING — MELONS, FRUIT-TREES, PEAS, CABBAGES, 



AND 



ON THE INCREASED SIZE OF HYBRID PLANTS, NOT 

 EXCLUSIVELY DUE TO THEIR STERILITY — ON CERTAIN PLANTS WHICH EITHER 

 NORMALLY OR ABNORMALLY ARE SELF-IMPOTENT, BUT ARE FERTILE, BOTH ON THE 

 MALE AND FEMALE SIDE, WHEN CROSSED WITH DISTINCT INDIVIDUALS EITHER OF 



114 



THE SAME OR ANOTHER SPECIES 



CONCLUSION 



