i 7 8 



ZOOLOGY. 



organs, and suggest the name of the group. There is a well-developed 

 stomodaeum. The gastro-vascular canal branches from this and is much 

 divided, one division lying under each row of combs. There are two 

 small aboral openings to the digestive canal known as excretory pores. 

 The mesenchyma is well developed. 



225. Notes on Coelenterates. The food of Coelenterates 

 consists largely of organic debris broken up by the waves, and 

 of small animals and plants captured by the tentacles. The 

 attached forms flourish best in the comparatively shallow 



FIG. 83. 



-r. 



FIG. 83. Hydractina Echinata, after Hincks. c, the ccenosarc, forming an incrusta- 

 tion over the object on which it lives; n, nutritive polyps; r, reproductive polyps, bear- 

 ing buds in which are ova; t, tentacles. 



Questions on the figure. How many types of individuals seem to be 

 represented? What evidence of budding do you see in the species? What 

 is the ccenosarc? What is its nature in Hydractina? What can you find 

 concerning the habits of the members of the genus ? How does this colony 

 compare with that in Fig. 84? 



water near the shore. Food is especially abundant in such 

 regions and hence the passive animals are more successful 

 here than elsewhere. Hydractina ( Fig. 83 ) and even the sea- 

 anemone form interesting partnerships with the hermit-crab. 



