12 ILLUSTRATIONS 



27. Graph Showing the Average Size of Litters Produced in Successive 



Generations of Inbreeding Albino Rats by Brother and Sister 

 Matings 109 



28. Goliath, an Albino Rat, the Product of Six Generations of the Closest 



Possible Inbreeding 110 



29. Representative Samples of Inbred Strains of Maize after Eleven 



Generations of Self-fertilization 130 



30. Graphs Showing the Reduction of Variability and Segregation of 



Ear Row Number in Selfed Strains of Maize 132 



31. Plants of Maize after Eleven Generations of Self-fertiUzation and 



Their Fi Hybrid 150 



32. Ears of Maize after Six Generations of Self-fertihzation and Their 



Fi Hybrid 150 



33. Graphs Showing Growth Curves of Two Inbred Strains of Maize and 



Their First and Second Generation Hybrids 152 



34. James River Walnut, Hybrid Between Persian Walnut and Butternut 154 



35. Growth Curves of Parent Races and Fi and F2 Hybrids of Guinea Pigs 160 



36. Diagram to Show How Factors Contributed by Each Parent May 



Enable the First Generation of a Cross to Obtain a Greater 

 Development than Either Parent 175 



37. Cattaloes, the Product of Crossing the Cow and the Bison 180 



38. Sterile Hybrid Between Radish and Cabbage 192 



39. Tassels of an Almost Sterile Strain Obtained by Inbreeding Maize . . 196 



40. Representative Ears of a Cross Between Two Inbred Strains of Maize 202 



41. Plants of a Cross Between Two Inbred Strains of Maize 202 



42. Diagram Showing a Method of Double Crossing Maize to Secure 



Maximum Yields, Illustrated by Actual Field Results 203 



43. First Generation Cross of Shropshire by Delaine Merino 212 



44. First Generation Cross of Hereford by Shorthorn 216 



45. "Big Jim" the Product of a Pure Bred Percheron Stallion Mated 



with a Grade Mare of the Same Breed 220 



46. First Generation Cross of Chester White and Poland China 224 



