viii CONTENTS 



CHAPTER IV 



PAGE 



Adaptation to Surroundings 73 



Crayfishes: Living Crayfish, 73 ; Morphology, 75 ; Sum- 

 mary, 79; Review and Library Exercise, 81. 



CHAPTER V 



Adaptation for Protection from Enemies ... 83 



Mollusca: Clam, 83; Snail, 87; Squid, 89; Comparative 

 Study, 91 ; Review and Library Exercise, 92. Comparative 

 Study of Exoskeletons, 93 ; Protective Coloration, 94 ; Ani- 

 mal Associations, 96; Protective Habits and Powers, 98; 

 Defensive Structures, 99 ; Thesis : " Adaptation for Protec- 

 tion,'' 99. 



CHAPTER VI 

 Vertebrates loi 



Fishes: Living Fish, loi ; External Structure, 103 ; Mouth 

 and Gills, 105 ; Alimentary Canal and Circulatory System, 

 107 ; Review and Library Exercise, 1 10. Primitive Chordates, 

 112. Amphibia: Living Frog or Toad, 114; Mouth, 116; 

 Organs of Digestion, Absorption, and Excretion, 1 17 ; Organs 

 of Circulation and Respiration, 120; Nervous System, 123; 

 Endoskeleton, 125 ; Comparative Study, 129 ; General Re- 

 view and Library Exercise, 129. Reptiles: Living Snake, 

 Lizard, and Turtle, 130 ; Review and Library Exercise, 132. 

 Birds: Living Pigeon, 133; Plumage, 136; Birds and Mi- 

 gration, 139; Laboratory Exercise, 139; Field Work, 141; 

 Review and Library Exercise, 142 ; Migration in General, 

 145. Mammals: Rodents: Domestic Rabbit, 146; Wild 

 Rabbit, 148; Guinea Pig or White Rat, 149; Squirrel, 150; 

 Library Exercise, 152. Carnivora: Laboratory Exercise, 

 153; Library Exercise, 155. Ungulates: Laboratory Exer- 

 cise, 157; Library Exercise, 160. The Horse, 162. Homol- 

 ogy of the Vertebrate Skeleton, 168. 



