CONTENTS. Vii 



i 



CHAPTER XXII. 



PADS 



OF THE CLASS OF ECHINODERMATA . . . ... 445 



ORDER I ECHINIDA. 446 



ORDER II. STELLERIDA . . . . ... 454 



ORDER III. FISTULIDA 461 



CHAPTER XXin, 



OF THE CLASS OF ACALEPH^ 468 



CHAPTER XXIV. 



OF THE CLASS OF POLYPIFERA 480 



ORDER L HVDKOIDA 482 



ORDER ll. HELIANTHOIDA 492 



ORDER III. A^TEROJDA . .... 516 



ORDER IV. OILIOBRACHIATA . 526 



CHAPTER XXV. 



OF THE CLASS OF POLYGASTRICA 540 



CHAPTER XXVI. 



OF THE CLASS OF PORIFERA 558 



APPENDIX. 



ON THE INSTINCTS CF SOCIAL INSECTS 567 



