Contents 



2-6 Senescence in wild populations 108 



2-6-1 Vertebrates 108 



2-6-2 Invertebrates 112 



3 SENESCENCE IN PROTOZOA 



3-1 Individual cells 114 



3-2 The 'senescence' of clones 116 



4 THE INFLUENCE OF GENETIC CONSTITUTION 



ON SENESCENCE AND LONGEVITY 



4-1 Inheritance of life-span 121 



4-1-1 General 121 



4-1-2 Parental age 125 



4-2 Heterosis or hybrid vigour 127 



4-3 Sex differences 130 



4-4 Progeria 134 



4-5 Choice of material for the experimental study of age 



effects 136 



5 GROWTH AND SENESCENCE 



5-1 'Rate of living' 138 



5-2 Experimental alteration of the growth rate 143 



5-2-1 Invertebrates 143 



5-2-2 Insect metamorphosis and senescence 146 



5-2-3 Vertebrates 148 



5-3 Growth-cessation and mammalian senescence 153 



6 THE MECHANISMS OF SENESCENCE 162 

 6-1 Senescence in cells 163 



6-1-1 'Irreplaceable' enzymes 163 



6-1-2 Cell turnover 166 



6-1-3 Somatic mutation 1 68 



6-1-4 Specificity 169 



6-2 Endocrine senescence 171 



6-2-1 General 171 



6-2-2 Gonad-pituitary system 177 



6-2-3 Hormonal regulation of growth in vertebrates. 1 82 



CONCLUSION 189 



BIBLIOGRAPHY 201 



INDICES 245 



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