CONTENTS. 



SECTION PAG 



I. THE STRUCTURE OF AAKEBA 1 



II. THE STRUCTURE OF PARAMCECIUM 7 



III. THE STRUCTURE OF VORTICELLA 12 



IV. THE MULTIPLICATION OF VORTICELLA . . . .19 

 V. CALCAREOUS SPONGE 22 



VI. THE STRUCTURE AND GROWTH OF THE ASEXUAL FORM 



OF A CAMPANULARIAN HYDROID 30 



VII. THE STRUCTURE OF AN OCELLATE HYDRO-MEDUSA . 37 



VIII. THE MEDUSA STAGE OF A CAMPANULARIAN HYDROID, 49 



IX. THE STRUCTURE OF A STARFISH : THE HARD PARTS . 56 



X. THE STRUCTURE OF A STARFISH: INTERNAL ANATOMY, 63 



XL THE MICROSCOPIC STRUCTURE OF THE STARFISH . . 73 



XII. THE HARD PARTS OF A SEA-URCHIN .... 83 



XIII. THE INTERNAL STRUCTURE OF A SEA-URCHIN . . 91 



XIV. THE EMBRYOLOGY AND METAMORPHOSIS OF ECHINO- 



DERMS 99 



XV. THE GENERAL ANATOMY OF THE EARTHWORM . . 140 



XVI. THE MICROSCOPIC STRUCTURE OF THE EARTHWORM . 152 



XVII. THE GENERAL ANATOMY OF THE LEECH . . .160 



XVIII. THE HARD PARTS OF THE COMMON CRAB . . .168 



XIX. THE HARD PARTS OF THE CRAYFISH OR LOBSTER . 185 



XX. THE GENERAL ANATOMY OF A CRAB . . . .190 



XXI. THE METAMORPHOSIS OF A CRAB . 207 



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