Vlll CONTENTS. 



CHAPTER VIII. page. 



The Crossing and the Close-Interbreeding of Pigeons and 

 of Fowls 242 



CHAPTER IX. 

 The Crossing and the Close-Interbreeding of Pigs . . . 280 



CHAPTER X. 

 The Crossing and Close-Interbreeding of Horses, Sheep 

 and Cattle . 298 



CHAPTER XI. 



The Crossing, and the Self- Fertilization, of Plants . . 334 



CHAPTER XII. 



Sterility of Hybrids 408 



CHAPTER XIII. 

 Concluding Remarks . . 429 



