LIST OF FIGURES 



Fig. I. Diagram of nuclear division. 



2. Two idants of Ascaris megalocephala. 



3. Diagram of the cell-generations in the fore-limb of a newt. 



4. Multiplication by fission in a marine worm {A/yriaiiida). 



5. Transverse section through the 'zone of gemmation' in a 



fresh-water worm (^iVais). 



6. An early stage in the formation of a bud in a Hydroid polype 



(^Eitdendruini) . 



7. Apex of a shoot of a fresh-water Alga (^Chara). 



8. Female water-flea {Daphnia) , with summer eggs. 



9. Nauplius larva of Leptodora hyalina. 



10. Alternation of generations in Botigainvillea. 



11. Strobilation of a Medusa. 



12. Degeneration of a Medusa into a mere gonophore. 



13. Early stages of development of the primitive germ-cells in 



Sagitta. 



14. Early stages in the development of the primitive germ-cells in 



Moina. 



15. Early stage of the embryo of Rhabditis nigrovenosa. 



16. Diagram of the germ-track in Rhabditis nigrovenosa. 



17. Volvox and Pandornia. 



18. Process of fertilisation in Ascaris megalocephala . 



19. Diagram to illustrate the composition of the idants out of 



individually different ids. 



20. Formation of spermatozoa in Ascaris viegalocephala. 



21. Formation of ova in Ascaris megalocephala. 



22. Diagram to illustrate the combination of idants in hybriils. 



23. The two varieties of Cypris reptans. 



24. Bonellia viridis, male and female. 



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