CHAPTER VII

THE ORDER APTERA—DEFINITION—CHIEF CHARACTERISTICS—THYSANURA—CAMPODEA —JAPYX—MACHILIS—LEPISMA—DIVERSITY OF INTERNAL STRUCTURE IN THYSANURA —ECTOTROPHI AND ENTOTROPHI—COLLEMBOLA—LIPURIDAE—PODURIDAE —SMYNTHURIDAE—THE SPRING—THE VENTRAL TUBE—ABDOMINAL APPENDAGES —PROSTEMMATIC ORGAN—TRACHEAL SYSTEM—ANURIDA MARITIMA—COLLEMBOLA ON SNOW—LIFE-HISTORIES OF COLLEMBOLA—FOSSIL APTERA—APTERYGOGENEA —ANTIQUITY AND DISTRIBUTION OF CAMPODEA 180