ILLUSTRATIONS 11 



49. The Same Chromosome Pair in Conjugation from Thirteen Different 



Cells 110 



50. Conjugation of an Unequal Pair of Chromosomes and Their Subse- 



quent Separation Ill 



51. Two Schemes Illustrating the Idea of Reduplication by Bateson 



and Punnett 116 



52. Scheme Illustrating How Double Crossing Over Between Two 



Distinct Genes takes Place 121 



53. Chromosome Groups of Pea, Wheat, and Primula 135 



54. Types of Chromosome Groups Found in Drosophila 136 



55. Haploid Group of Chromosomes of the Silkworm Moth 137 



56. Curve Showing Influence of Crossing Over at Different Temperatures 142 



57. Diagram Illustrating the Effect on Crossing Over Due to the Presence 



of Crossover Genes 143 



58. Chromosome Group of (Enothera Lamarckiana and 0. gigas, and 



Triploid Group 149 



59. Life Cycle of Moss 152 



60. Diagram Illustrating the Formation of Individuals from the Regener- 



ation of the Sporophyte in a Dioecious Species 153 



61. Diagram Illustrating the Formation of Individuals from the Regener- 



ation of the Sporophyte in a Hermaphroditic Species 153 



62. Somatic Chromosomes Groups of (Enothera sdntillans 156 



63. Scheme Showing the Probable Relation Between the Extra Chromo- 



some Pieces of Fig. 62, and the Normal Fifteen Chromosomes of 

 This Mutant 158 



64. An Egg of Ascaris hivalens Fertilized by Sperm of A. univalens .... 160 



65. Diploid and Haploid Groups of the Sundew Drosera 160 



66. A Scheme Illustrating the Fertilization of the Egg of One Species of 



Moth by the Sperm of Another 161 



67. Scheme Illustrating the History of the Chromosomes, and the Back- 



cross Between a Hybrid Male and One or the Other Parent .... 162 



68. Scheme Showing the Relation of the Sex- Chromosome to Sex-De- 



termination 166 



69. Cross Between White-Eyed Male and a Red-Eyed Female of the 



Vinegar Fly 168 



