CONTENTS xi 



CHAPTER V 



PAGE 



THE CHROMOSOMES . .123 



A. THE CONTINUITY OF THE CHROMOSOMES . . .124 



B. THE COMPOSITION OF THE CHROMOSOMES OF SMALLER UNITS . 134 



C. VARIATION IN THE NUMBER OF CHROMOSOMES . . .138 



1. Variation i?i Chromosome Number due to Fragmentation 



or Linkage . . . . . 1 3 9 



2. Variation in Chromosome Number due to Irregularities 



of Mitosis . . . . . .144 



3. Variation in Chromosome Number due to Multiplication 



or Fusion . . . . .147 



CHAPTER VI 



HEREDITY AND MORPHOGENESIS . . . . 153 



A. THE EQUALITY OF INHERITANCE FROM MALE AND FEMALE 



PARENTS . . . . . . 154 



B. THE PROCESS OF MITOSIS AND ITS IMPLICATIONS. THE. 



FUNCTIONAL DIFFERENTIATION OF THE CHROMOSOMES . 162 



C. THE PROCESS OF MEIOSIS . . . . .167 



D. THE PARALLEL WHICH EXISTS BETWEEN CHROMOSOME BE- 



HAVIOUR AND THE RESULTS OF BREEDING EXPERIMENTS . 168 



1. The f Genetics of a Tetraploid Plant . . .170 



2. Segregation and Parthenogenesis . . -17* 



3. Segregation and Bud-Variation . . .172 



4. The Interchange of Hereditary Factors between Homo- 



logous Chromosomes . . . . .174 



5. The Cytological Basis of Mutation . . .186 



E. STERILE AND PARTIALLY STERILE HYBRIDS . . .183 



F. THE NUCLEUS IN MORPHOGENESIS . . .187 



G. CHROMIDIA AND CHONDRIOSOMES . . . .190 



1. Chromidia . . . . . .190 



2. Chondriosomes . . . . . J 95 



3. The Relatio7i between Chromidia and Chondriosomes . 200 



