xil CONTENTS 



CHAPTER III 



PAGE 



AN INTRODUCTION TO THE METAZOA 73 



1 . Germ Cells and Somatic Cells 73 



2. Tissues .......... 74 



3. Organs and Systems of Organs . . . .76 



4. Reproduction ......... 79 



5. The Forms of Animals .90 



CHAPTER IV 



PHYLUM PORIFERA . . 92 



1. Structure of a Simple Sponge Leucosolenia . . . 92 



2. Anatomy and Physiology of Grantia .... 94 



3 . The Fresh-water Sponge Spongilla .... 98 



4. Sponges in General ........ 99 



CHAPTER V 



PHYLUM CCELENTERATA 108 



1. The Fresh-water Polyp Hydra 108 



2. Class I. Hydrozoa . . . . . . . .118 



a, A Colonial Hydrozoon Obelia, 119; b, Metagene- 

 sis, 122 ; c, A Jellyfish or Medusa Gonionemus, 122 ; 

 d, Hydroid and Medusa Compared, 124 ; .e, Polymor- 

 phism, 126; f, Reproduction in the Hydrozoa, 127; 

 g, Classification of the Hydrozoa, 128. 



3. Class II. Scyphozoa 129 



a, A Scyphozoan Jellyfish Aurelia, 129; b, Classifi- 

 cation of the Scyphozoa, 132. 



4. Class III. Anthozoa 133 



a, A Sea Anemone Metridium, 134 ; b, A Coral Polyp, 

 137 ; c, Coral Reefs and Atolls, 138 ; d, Classification 

 of the Anthozoa, 139. 



5. Crelenterates in General 142 



CHAPTER VI 

 PHYLUM CTENOPHORA 145 



