TEXT FIGURES 



rCUKE PAGE 



1. Nucleus and cytoplasm in Acetahulciria 17 



2. Hybrid and merogon sea-urchins 18 



3. The chromosome cycle in sexual reproduction 24 



4. The chromosomes of Drosophila and Crocus 26 



5. The salivary gland chromosomes of Droiop/ii'/a 27 



6. Meiosis and crossing-over 32 



7. Segregation in peas 39 



8. Recombination in Chlamydomonas 44 



9. Maps of the X. chromosome in Drosophila melanogaster 47 



10. Sex-linked inheritance 48 



11. Autosexing in poultry 50 



12. Partial sex-linkage in fishes 51 



13. The sex chromosomes of Dro50/)/!i7a and man 53 



14. The normal frequency distribution of stature in man 57 



15. Relation between genotype and phenotype in polygenic in- 

 heritance 67 



16. Polygenic segregation in Epilachtia 69 



1 7. Segregation for corolla length in Nkotiana 71 



18. The components of variation in height of Antirrhinum plants 87 



19. The origin of triploids in Ascaris 97 



20. The results of chromosome breakage and reunion loi 



21. The Bar duplication in Drosophila io8 



22. Chimaeras in So/aHKWi iii 



23. A gynandromorph in Drosophila 112 



24. The modes of origin of gynandromorphs 113 



25. Pleiotropic action of a lethal gene in the rat 116 



26. The Agouti series of allelomorphs in the mouse 118 



27. Meiosis in polyploids 122 



28. The pollen grain chromosomes of Crepis capillaris 124 



29. Interchange, and meiosis in the interchange hybrid 128 



30. Chromosome pairing in structural hybrids 129 



31. Inversion distinguishing Drosophila melanogaster and sinnilaiis 131 



32. Pachytene pairing and linkage map of Oenothera 133 



33. Chromosome balance in Raphano-brassica 136 



34. Polyploidy in Aescuhis 138 



35. Segregation and fertihty in polyploids 140 



36. Genes, chromosomes and nucleo-proteins 148 



37. The A, B, O system of blood groups in man 153 



38. The interactions of two genes 156 



39. The synthesis of tryptophane in NeMro5porrt 162 



40. The four relations of genes in action 165 



41. Plastid inheritance in barley 172 



42. The inheritance of Killer in Parameciutn 176 



43. The inheritance of meUbiose fermentation in yeast 180 



44. Dauermodification in Phaseohis 184 



II 



