CONTENTS. Vll 



CHAPTER XXII. 



PACK 



OF THE CLASS OF ECHINODERMATA 445 



ORDER I. ECHINIDA . 446 



ORDER II. STELLERIDA 454 



ORDER HI. FISTULIDA 461 



CHAPTER XXIII. 



OF THE CLASS OF ACALEPH^E ....... 468 



CHAPTER XXIV. 



OF THE CLASS OF POLYPIFERA 480 



ORDER I. HYDROIDA 482 



ORDER II. HELIANTHOIDA 492 



ORDER III. ASTEROID A 516 



ORDER IV. CIUOBRACHIATA 526 



CHAPTER XXV. 



OF THE CLASS OF POLYGASTRICA . 540 



CHAPTER XXVI. 



OF THE CLASS OF PORIFERA ........ 558 



APPENDIX. 



ON THE INSTINCTS OF SOCIAL INSECTS .... 567 



