iv CONTENTS. 



NEWLY-ACQUIRED CHARACTERS IN OUR DOMESTICATED ANIMALS 

 OFTEN TRANSMITTED BY ONE SEX ALONE, SOMETIMES LOST BY ONE 

 SEX ALONE — INHERITANCE AT CORRESPONDING PERIODS OF LIFE — 

 THE IMPORTANCE OF THE PRINCIPLE WITH RESPECT TO EMBRY- 

 OLOGY ; AS EXHIBITED IN DOMESTICATED ANIMALS ; AS EXHIBITED 

 IN THE APPEARANCE AND DISAPPEARANCE OF INHERITED DIS- 

 EASES; SOMETIMES SUPERVENING EARLIER IN THE CHILD THAN 

 IN THE PARENT — SUMMARY OF THE THREE PRECEDING CHAPTERS. 



Pages 37-61 



CHAPTER XV. 

 ON CROSSING. 



FREE INTERCROSSING OBLITERATES THE DIFFERENCES BETWEEN ALLIED 

 BREEDS — WHEN THE NUMBERS OF TWO COMMINGLING BREEDS ARE 

 UNEQUAL, ONE ABSORBS THE OTHER — THE RATE OF ABSORPTION 

 DETERMINED BY PREPOTENCY OF TRANSMISSION, BY THE CON- 

 DITIONS OF LIFE, AND BY NATURAL SELECTION — ALL ORGANIC 

 BEINGS OCCASIONALLY INTERCROSS ; APPARENT EXCEPTIONS — ON 

 CERTAIN CHARACTERS INCAPABLE OF FUSION ; CHIEFLY OR EX- 

 CLUSIVELY THOSE WHICH HAVE SUDDENLY APPEARED IN THE IN- 

 DIVIDUAL — 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 CROSS- 

 ING OF DISTINCT SPECIES IN RELATION TO THE FORMATION OF 

 DOMESTIC RACES 62-77 



CHAPTER XVI. 



CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF 

 VARIETIES — INFLUENCE OF DOMESTICATION ON FER- 

 TILITY. 



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 



