Xll 



CONTENTS 



CHAPTER III 



AN INTRODUCTION TO THE METAZOA 



1 . Germ Cells and Somatic Cells . 



2. Tissues ...... 



3. Organs and Systems of Organs 



4. Reproduction . 



5. The Forms of Animals . 



PAGE 



73 

 73 

 74 

 76 



79 

 90 



CHAPTER IV 



PHYLUM PORIFERA 



1. Structure of a Simple Sponge Leucosolenia . 



2. Anatomy and Physiology of Grantia 



3. The Fresh-water Sponge Spongilla 



4. Sponges in General ...... 



92 



92 



94 

 98 



99 



PHYLUM CCELENTERATA 



CHAPTER V 



Hydra 



1 . The Fresh-water Polyp 



2. Class I. Hydrozoa 



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

 sis, 122 ; c, A Jellyfish or Medusa- Gonioneiniis, 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 ....... 



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

 cation of the Scyphozoa, 132. 



4. Class III. Anthozoa 



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

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

 of the Anthozoa, 139. 



5. Ccelenterates in General . 



108 

 1 08 



118 



129 



133 



142 



CHAPTER VI 



PHYLUM CTENOPHORA 



145 



