LIST OF ILLUSTRATIONS 



PIG. PAGE 



1. OVUM OF A THREADWORM (FROM CARNOY) .... 5 



2. DIAGRAM OF CELL DIVISION (AFTER BOVERI) . . . . 31 



3. DIAGRAM OF CELL STRUCTURE (AFTER WILSON) . . .33 



4. " COMET-FORM " OF STARFISH (AFTER HAECKEL) 35 



5. ASEXUAL REPRODUCTION OF A SEA-WORM (AFTER MC!NTOSH) , 36 



6. DIAGRAM OF OVUM AND SOMATIC CELL (AFTER CARNOY) facing 38 



7. VOLVOX GLOBATOR . ... . . . . 39 



8. FORMS OF SPERMATOZOA . . . . . . . 41 



9. DIAGRAM OF GERMINAL CONTINUITY (AFTER WILSON) . . 43 



10. PARALLELISM OF SPERMATOGENESIS AND OOGENESIS (AFTER 



BOVERI) . . .... . . . . 47 



11. DIAGRAM OF REDUCTION AND AMPHIMIXIS (AFTER ZIEGLER) facing 48 



12. FERTILISED OVUM OF ASCARIS (AFTER BOVERI) ... i 49 



13. DIAGRAM OF MATURATION AND FERTILISATION (FROM ZIEGLER). 



facing 51 



14. CHROMATIN ELEMENTS OF NUCLEI (AFTER PFITZNER) . . 59 



15. DIAGRAM OF FERTILISATION IN ASCARIS (AFTER BOVERI) . 60, 61 



16. A POLLEN GRAIN WITH ITS NUCLEI (FROM CARNOY) ... 63 



17. DIAGRAM TO ILLUSTRATE THE DIFFERENCE BETWEEN MODIFICA- 



TIONS AND VARIATIONS 71 



1 8. VARIETIES OF WALL-LIZARD (AFTER EIMER) .... 74 



19. VARIATIONS IN WASP (AFTER KELLOGG AND BELL) . facing 76 



20. VARIATIONS IN BEETLE (AFTER TOWER) ... ,,76 



21. MUTATION IN MEDUSOIDS . ...... 89 



22. MUTATIONS OF HART'S TONGUE FERN (AFTER LOWE) . facing 98 



23. KARYOKINESIS (AFTER FLEMMING) . 102 



24. LEAVES OF WILLOW (AFTER WIESNER) . . . . . in 



25. DEVONSHIRE PONY WITH STRIPES (FROM DARWIN) . . .121 



26. VARIETIES OF DOMESTIC PIGEON (AFTER DARWIN) . . 139 



27. BRINE-SHRIMP, ARTEMIA SALINA 213 



273. TAIL-LOBES OF ARTEMIA SALINA (AFTER SCHMANKEWITSCH) . 213 



28. HALF-LOP RABBIT (FROM DARWIN) . . . . 289 



xv 



