﻿xiv CONTENTS. 



CHAPTER XX. 



PAGE 



Worms , . . . . . . . .153 



Angle Worms, 154 ; How they move, 15-1, 155 ; Leech, 155 ; Sea- Worms, 156, 157 ; 

 Tube-building Worms, 159. 



CHAPTER XXI. 



Concerning Natural Groups . . . . . . 1 60 



Characters of Articulates, 160 ; Of Worms and Mollusks, 161 : Type Characters, 161 ; 

 Tyi»ical Animals, 16'Z ; Systematic Tables and Classification, 163. 



I 

 CHAPTER XXII. 



Characters of Vertebrates . . . . . .103 



External Characters of Salamanders, 163, 164; Comparison with Cat, 165; Differ- 

 ences between the two, 166; Young Salamander, 166; Skeleton of Cut. 167; 

 Vertebral Column and Spinal Cord, K'9, 17D; Bones of the Ankle and Wrist, 

 171, 172; Groups of Vertebrates, 173, 174. 



CHAPTER XXIII. 



Bones of the Leg and Wing of Birds ..... 1*74 



Importance of studying Young Forms. 174; Wing Bones of an Adult Bird. 175; 

 Embryo Birds, and WingBof^es of same, 176; Leg Bones of an Adult Bird, 

 177; Leg Bones of Embryo Bird, 178; Leg Bones of Young Toad, ISO. 



CHAPTER XXIV. 



Classes and Sub-Kingdoms . . . . . .181 



Sub-Kingdom Mollusca, Class Gasteropoda, 181; Class Acephala, 182; Sub-King- 

 dom Arthrnpoda, Class Insecta, 183 ; Class Myriopoda, 184 ; Class Arachnida, 

 185 ; Sub-Kingdom Vermes, Class Annelida, 185 ; Class Crustacea, 186 ; Sub- 

 Kingdom Vertebrata, 187. 



Notice to Teachers . . . . . . . 189 



