Contents. 



CHAPTER PAGE 



XXI. BRANCH ECHINODERMATA . . . . . . .331 



Class i. Asteroidea . 331 



Class 2. Ophiuroidea ....... 337 



Class 3. Echinoidea . 338 



Class 4. Holothuroidea 343 



Class 5. Crinoidea 345 



XXII. BRANCH PLATYHELMINTHES The Flatworms . . . 348 



BRANCH NEMATHELMINTHES The Roundworms . . . 351 



BRANCH TROCHELMINTHES The Rotifers . . . . 352 



BRANCH MOLLUSCOIDA . . 353 



XXIII. CLASSIFICATION OF THE ANIMAL KINGDOM .... 355 



INDEX . . -359 



