184 ELEMENTARY ZOOLOGY. 



Polyps and medusa-like bodies united in a floating or free- 

 swimming colony Order Siphonophora. 



Example; Portuguese Man-of-war (Physalia). 

 Mouth, with ectodermal gullet leading to gastro- vascular cavity 

 more or less divided by partitions. 



Chiefly medusoid (jelly-fishes) Class II Scyphozoa. 



Examples: Aurelia, Lucernaria. 



Chiefly polyps Class III Anthozoa. 



With partitions on plan of 6 Sub-class Hexacoralla. 



Solitary; no skeleton. Example: Sea Anemones. 



Limy skeleton. Examples: Reef-forming corals, as Ma- 



drepora, Astrcea, etc. 



Partition on plan of 8 Sub-class Octocoralla. 



Examples: Red Coral; "Dead-men's Fingers;" sea-fans. 

 Nettling cells modified into "adhesive cells"; jelly-like, 



Class IV Ctenophora. 



203. Topics for Themes in Zoology and English. i. 



Discuss the power of regenerating lost parts in Hydra 

 and other species of ccelenterates. The value and mean- 

 ing of it. 



2. Coral reefs kinds and manner of formation. Kinds 

 of corals that take part in this work. 



3. Compare the different forms of organic colonies 

 illustrated in this branch. Arrange them by beginning 

 with the simplest and going to the most complex. What 

 is the most complex instance that you are able to find? 



4. Polymorphism and division of labor in the colonies. 

 What different. functions are apportioned to the different 

 individuals? Which are retained by each individual? 



5 . What convinces you that the Portuguese man-of-war 

 is a colony rather than an individual with complex 

 organs? 



6. Select some type, as Obelia, Campanularia, Pennaria, 

 or Aurelia, and follow the life-cycle carefully in the 

 reference books, studying the alternation of generation. 

 Examine all the figures you can find of the species. 



