JO Laboratory Guide in Zoology 



typical and easily understood. Their structure is well 

 illustrated by the common Fresh-water Hydra. Members 

 of this class reproduce by budding, sometimes by fission, 

 and sometimes by eggs. Many marine jelly-fishes belong 

 to this class, although a majority of the large jelly-fishes 

 are included in the second class, the Scyphozoa, and a few 

 peculiar forms known as Comb-jellies are included in the 

 Ctenophora, which forms the fourth and highest class of 

 the Coelenterata. 



The members of the third class, called the Actinozoa, 

 greatly resemble, and were long thought to be, marine 

 plants. Here belong the sea-anemones and other soft- 

 bodied polyps. The coral polyps, which secrete a kind 

 of calcareous framework, also belong to this class. These 

 animals, living a fixed life, constantly reproducing by fis- 

 sion, have been the chief agency in building up our vast 

 coral reefs and islands. 



