CHAP. 



PREFACE 



PAGE 

 V 



I INTRODUCTION TO CYCLES 



II CYCLES OF REPRODUCTION 



I. Introduction: 2. Seasonal cycles in tem- 

 perate regions: 3. The effects of latitude: 

 4. The effects of domestication: 5. Oestrous 

 cycles: 6. Conclusions 



III THE ENVIRONMENT AND REPRODUCTION 



I. The nature of seasonal cycles: 2. Evidence 

 from the movements of animals: 3. Environ- 

 mental factors: 4. The effects of light: 5. 

 Limitations of the light control theory: 6. 

 Autumn-breeding animals: 7. Conclusions 

 regarding the action of light: 8. The question 

 of the tropics: 9. The various external factors 

 which affect breeding: 10. Psychological 

 factors in reproduction: 11. Conclusions 



20 



IV HORMONES AND REPRODUCTION 



I. Introduction: 2. The pituitary gland: 3. 

 The hormones of the anterior pituitary: 4. 

 The testis: 5. The testis hormones: 6. The 

 ovary: 7. The ovarian hormones: 8. The 

 oestrous cycle: 9. The seasonal cycle: 10. The 

 problem of internal reproductive rhythms: 



II. The influence of the environment: 12. 

 Conclusions 



V SEXUAL BEHAVIOUR 



I. Introduction: 2. The gonads and sexual 

 behaviour: 3. Hormones and sexual behaviour: 

 4. The special problem of migration: 5. 

 Conclusions 



45 



80 



