CONTENTS. 



CHAPTER I. 



THE INTERDEPENDENCE OF ORGANISMS. 

 I. THE RELATIONS BETWEEN FLOWERS AND INSECTS, p. 7. i. 

 The adaptation of flowers to insect visitation, p. 1 1 . 2. The 

 adaptation of insects to flower visitation, p. 17. How to 

 know the orders of flower insects, p. 24. 3. The relative fit- 

 ness of the different visitors to one kind of flower, p. 26. 4. 

 The relative fitness of the different flowers visited by one 

 kind of insect. to profit by its visitation, p. 28. 5. Precise 

 adaptation between flowers and insects, leading to mutual 

 dependence, p. 29. 6. Specialization miscarried, p. 32. 

 II. GALLS, p. 35. Animal galls, p. 38. The animals that produce 

 galls, p. 42. Key to the commoner insects larvae and mites 

 found in galls, p. 45. 



III. THE RELATIONS BETWEEN ANTS AND APHIDS, p. 47. The 

 chance feeding by ants on the honey dew offered by aphids, 

 p. 48; The habitual guarding of aphid colonies by ants, p. 49. 

 The domestication of aphids by ants, p. 50. 



PRACTICAL EXERCISES. 



Study i . Flowers adapted to insect visitation, p. 14. 

 Study 2. Insects adapted to visiting flowers, p. 24. 

 Study j. The relative fitness of the different visitors to one kind of 



flower, p. 26. 

 Study 4. An examination of all the flrwers visited by some common 



insect, p. 28. 



Study 5. A case of precise adaptation, p. 32. 

 Study 6 . A study of common galls, p. 46. 

 Study 7- Observations on ants and aphids, p. 54. 



CHAPTER II. 

 THE SIMPLER ORGANISMS. 

 I. SOME TYPICAL ALG/E, p. 56. The cell, p. 61. The form of the 



plant body in common algae, p. 64. 

 II. Some typical protozoans, p. 68. 



