viii Contents 



CHAPTER VI 



PAGE 



EXPERIMENTAL HYBRIDIZING 66 



Mendel's Law 66 



Mendel's Law and the Germ-cells 72 



CHAPTER VII 



EXPERIMENTAL HYBRIDIZING (Continued) 82 



Experiments with Mice 82 



CHAPTER VIII 

 EXPERIMENTS WITH OTHER MAMMALS AND WITH BIRDS .... 99 



Experiments with Guinea Pigs ........ 99 



Experiments with Rabbits 106 



Experiments with Rats . . . . . . . . .no 



Experiments with Cats 113 



Data for Other Mammals and Man . . . . . . .116 



Experiments with Poultry 121 



Experiments with Pigeons . . . . . . . . .135 



CHAPTER IX 



EXPERIMENTS WITH SNAILS, MOTHS, AND BEETLES 139 



Experiments with Silkworms ........ 141 



Experiments with Beetles 151 



Experiments with the Currant Moth . . . . . . 153 



Experiments with Tephrosia 153 



CHAPTER X 



OTHER KINDS OF HYBRIDIZING 156 



Blended Inheritance 156 



Mosaic Inheritance 157 



Hybridization between Linnaean Species 157 



Dimorphism 160 



Reversal of Symmetry 165 



Conclusions regarding Mendelian Inheritance 1 66 



CHAPTER XI 



BEHAVIOR OF THE GERM-CELLS IN CROSS- FERTILIZATION . . . .173 



Experiments with Amphibia 173 



Experiments with Echinoderms 175 



Factors involved in the Entrance of the Spermatozoon . . .178 



Artificial Helps to Fertilization and to Cross-fertilization . . .181 

 Polyspermy ............ 182 



