Growth of Hydroid Colonies. 



37 



into a stomach, from which four tubes radiate to the 

 margin of the bell, where they are united by a circular 



FIG 22. 



Physalia or Portuguese Man of War : a, b, c, three stages of growth : a', air- 

 sac or float ; TT polypites, T tentacles ; d tentacle showing the clustered 

 masses of thread-cells. 



canal, in the walls of which, or within the wall of the 

 stomach, the eggs are formed. 



