viii CONTENTS 



CHAPTER PAGE 



X. Starfish 74 



A. Structure 74 



B. Organ Systems 76 



1. Nutritive System . . . . . .76 



2. Water Vascular System 76 



3. Respiratory, Excretory, and Vascular Systems . 78 



4. Reproductive System 79 



5. Nervous System 79 



XI. Earthworm 81 



A. External Structure 82 



B. Organ Systems 84 



1. Nutritive System . . . . . . .85 



2. Vascular System 87 



3. Respiratory System 90 



4. Excretory System 91 



5. Reproductive System 92 



6. Nervous System 95 



XII. Crayfish 99 



A. External Structure 99 



B. Structure of the Appendages 100 



C. Organ Systems 104 



1. Nutritive System 104 



2. Vascular System 105 



3. Respiratory System 107 



4. Excretory System 108 



5. Reproductive System 108 



6. Nervous System 110 



XIII. Insects 113 



I. Grasshopper 114 



A. External Structure 114 



1. Head 114 



2. Thorax 116 



3. Abdomen 117 



B. Organ Systems 117 



1. Nutritive System 118 



2. Respiratory and Vascular Systems . . . .119 



3. Excretory System 120 



4. Reproductive System 120 



5. Nervous System 123 



II. Honeybee 123 



A. External Structure 123 



1. Head 124 



2. Thorax 125 



3. Abdomen 127 



