QUESTIONS. 355 



76. Give the leading characters of the Actinozoa. 



77. How does the transverse section of a Hydrozoon differ from that of 

 an Actinozoon ? 



78. What is a "polype?" 



79. Describe a Sea-anemone. 



80. What are the "mesenteries " of a Sea-anemone, and what organs do 

 they carry ? 



81. What is a " coral ? " 



82. What are the " septa " of a coral, and to what part of the living 

 animal do they correspond ? 



83. What are coral-reefs, where do they occur most abundantly, and what 

 are the chief varieties which occur ? 



84. How do the Alcyonaria differ numerically from the Zoantharia ? 



85. Mention some example of the Alcyonaria. 



86. In what Alcyonarian is there a well-developed sclerodermic coral ? 



87. Of what nature is the sclerobasic coral of the Gorgonidce? 



88. Mention a well-known example of the Gorgonidce. 



89. Give the leading characters of the Ctenophora. 



90. What is a " ctenophore ? " 



91. Is a nervous system present in any of the Actinozoa, except in the 

 Ctenophora ? 



92. Mention an example of the Ctenophora. 



93. What animals belong to the Echmodermata, and whence is the name 

 of the class derived ? 



94. What is understood by " bi-lateral symmetry ? " 



95. At what time of life are the Ecliinoderms bi-laterally symmetrical, 

 and what is their condition in this respect when adult ? 



96. What is a water-vascular system, what is it called in this class, and 

 what special function does it generally discharge ? 



97. What is the arrangement of the nervous system in Echinoderms ? 



98. What distinguishes the Sea-urchins from other Echinoderms ? 



99. Into how many zones may the test of a living Sea-urchin be divided, 

 and how many rows of plates are contained in each zone? 



100. What are the " ambulacral " and " inter-ambulacral areas ? " 



101. What plates are always placed at the summit of the shell ? 



102. What is the " madreporiform tubercle ? " 



103. Describe the general nature of the spines and their function. 



104. What are " pedicellariae ? " 



105. What are the " tube-feet ? " Describe the general arrangement of 

 the u ambulacral system." 



106. What is the structure of the circulatory and nervous organs in the 

 Echinus ? 



107. Mention a peculiarity in the development of the Echinus. 



108. Give the leading characters of the Star-fishes. 



109. What peculiarities distinguish the arms of Star-fishes ? 



110. What is the structure of the stomach in Star-fishes ? 



111. How do the Brittle-stars resemble the true Star-fishes, and how are 

 they distinguished ? 



112. What is the structure of the digestive system in Brittle-stars? 



113. What is the essential peculiarity of the "Crinoids? 



114. Mention a living Crinoid which is free when adult, and one which is 

 permanently fixed. 



115. What is the general shape of the Holothurians, and the nature of 

 their integuments ? 



