RADIATA. 



179 



pair of partitions, so that the skeleton ot a single 

 polyp (or corallite) is a short tube with vertical septa 



FIG. 79. Corals. 



radiating toward the center. The Fungia, or Mush- 

 room coral, is disk- 

 shaped, and differs 

 from others in not 

 being either fixed or 

 compound. It is sim- 

 ply the skeleton of a 

 single polyp, showing 

 a radiating secretion 

 of calcareous septa. 

 The various kinds of 

 budding in compound 

 coral-polyps give ris- 

 to a variety of shapes, 

 either dome -like or FIG. 8o,-Madrepore. 



