GYMNOBLASTEA 



157 



form the enteron. From the base of this first formed polyp there is 

 an outgrowth along the surface of attachment which is the beginning 

 of the hydro rhiza. From this the rest of the colony is developed. 



Fig. 116. Bougainvillea fructuosa, x about 12. From AUman. A, The fixed 

 hydroid form with numerous hydroid polyps and medusae in various stages 

 of development. B, The free-swimming sexual medusa which has broken 

 away from A. 



In Bougainvillea (Fig. 116) the polyps belong to the gymnoblastic 

 type to be described for Tubularia. The creeping hydrorhiza gives 

 off branches, one of which is seen in the figure, and from these 



