LIST OF PLATES 



Microphotographs of li\ing and fixed cells in sectioned and smear 

 preparations. 



PAGE 



I. Root-tips of Crepis dioscoridis and C. capillaris . . .22 



II. Pollen-grains of Par-is qiiadrifolia ...... 46 



III. Mitosis in animals and plants, i and 2. Testes of Chorthippus 



parallelus 



3. Testis of Locusta migratoria 



4. Root-tip of Eremurus spectabilis 



5 and 6. PoUen grains of Tradescantia hracteata and Brodiaea 



iiniflora 

 7 and 8. Root-tips of Puschkinia libanotica and Tricyrtis hirta. 78 



IV. First metaphase of meiosis showing major spirals in Hyacinthus 



orientalis, Tradescantia virginiana, and T. rubra . . 118 



V. Pollen mother-cells of triploid plants, i and 2, zygotene in 



Tulipa. 3, First division in Fritillaria .... 126 



VI. First metaphase in pollen moter-cells of interchange hybrids : 



Campanula, Rhceo, CEnothera and Pisum . . .152 



VII. Salivary gland chromosomes in Diptera, Chironomus and 



Drosophila . . ... . . . . .178 



VIII. Secondary pairing at first and second metaphase of meiosis 

 in pollen mother-cells of polyploid plants. Cydonia, 

 Pentstemon, Dahlia, Prunus, ^sculus . . . .236 



IX. Results of Crossing-over in inversion heterozygotes, animal and 



plant : Chorthippus, Tulipa, Pcsonia, Podophyllum . .274 



X. 1-5. Meiosis in Phragmatobia 



6. Sex chromosomes in Melandrium 



7. Meiosis in monosomic Zea Mays 



8 and 9. Polymitosis in pollen grains of Zea Mays . . . 358 



XI. Sex chromosomes in Chorthippus (Orthoptera), Hemerobius 



(Neuroptera), Putorius, man and the rat (Mammalia) . 388 



XII. Mitosis showing the formation of dicentric chromatids follow- 

 ing X-ray treatment and crossing-over in inversions : 

 Tulipa, Crocus, Allium, Vicia ..... 430 



