TWO-LAYERED ANIMALS— PHYLUM COELENTERATA 



125 



Another interesting example of the Hydrozoa is a comparatively large 

 marine form commonly called the Portuguese man-o-war, with the scien- 

 tific name of Physalia. Its common name is derived from the fact that it 

 has an air-filled membrane which acts as a float that stays on top of the 



Courtesy New York Zoological Society 



Fig. 9.6. Physalia, the Portuguese man-o-war. The float is filled with air and stays 



on the surface, while the long tentacles, armed with powerful stinging cells, trail out 



in the water beneath. This one has stung a fish into insensibility and has pulled it up 



close to the feeding polyps where it is being digested and absorbed. 



