THE ANIMAL KINGDOM. 171 



85. Describe the Rotifera. 



86. What are the ' distinguishing features of the Mol- 

 lusca ? Name the leading groups of them. 



87. How do the shells of the Conchifera differ from 

 those of the Gasteropoda ? 



88. What is understood by the term Radiata ? 



89. Describe the Echinus. 



90. What are the Acalephas ? 



91. What is meant by the Polypifera? 



92. Describe and sketch the Fresh-water Hydra. 



93. Give an account of the formation of Madrepores. 



94. How does this formation differ from that of Corals ? 



95. To what group of animals do Corals belong? 

 Whence and how are they obtained ? 



96. What are the Tubipora ? 



97. What is meant by Protozoa ? 



98. What are the Rhizopoda ? 



99. What is the difference between Foramenifera and 

 Polycystina ? 



100. Describe the formation of sponges. 



