ILLUSTRATIONS 



FIG. PAGE 



1. Photograph of John Shell, claimed to be 131 years old, but actually 



about 100, with his wife and putative son (From Nascher) 26 



2. Showing the changes in nerve cells due to age (From Donaldson 



after Hodge) 29 



3. Paramecium, viewed from the oral surface (From Jennings) 31 



4. Diagram showing the process of reproduction by fission in the uni- 



cellular organism Paramecium 32 



5. Conjugation in Paramecium 32 



6. Planaria dorotocephala (From Child) 34 



7. Beginning of process of agamic reproduction by fission in Planaria 



(From Child) 35 



8. Progress of agamic reproduction in Stenostomum (From Child) .... 36 



9. Section across the posterior part of an embryo dog-fish (Acanthias) 



of 3.5 mm. (From Minot after Woods) 38 



10. First and second division in egg of Cyclops (From Child) 39 



11. Diagram to show mode of descent (Modified from Jennings) 41 



12. Artificially parthenogenetic frogs (Loeb) 52 



13. Piece of tissue from frog embryo cultivated in lymph (From Harrison) 58 



14. Group of nerve fibers which have grown from an isolated piece of 



neural tube of a chick embryo (From Harrison after Burrows) .... 59 



15. Human connective tissue cells fixed and stained with Giemsa stain 



(After Losee and Ebeling) 60 



16. Pennaria (From Wilson) 62 



17. Culture of old strain of connective tissue (Ebeling) 63 



18. Life table diagram 81 



19. Comparing the expectation of life in the 17th century with that of 



the present time 84 



20. Comparing the expectation of life in the 18th century with that of 



the present time 86 



21. Comparing the expectation of life of ancient Egyptians with that of 



present day Americans 88 



22. Comparing the expectation of life of ancient Romans with that of 



present day Americans 90 



13 



