THE SEA SHORES 1 77 



more tentacles armed with formidable stinging organs, or of 

 such units intermixed with other types modified from them, 

 borne upon a flattened, wand-like, or tree-like support. The 

 units vary from very small, in the hydroids and millepores, 

 to an inch or so in diameter; in the non-colonial forms they 

 may be more than a foot across. The stinging organs, which 

 paralyze as well as sting the prey, enable the coelenterates to 

 use as food much larger and stronger creatures than do any 

 other of the animals which feed in this way, and they are 

 wholly carnivorous. The coelenterates support many parasites, 

 especially crustaceans which live within their bodies or travel 

 up and down their stems appropriating the food which they 

 have collected, and brittle-stars especially adapted for cling- 

 ing to them, while many animals attach themselves to them 

 which are known to live nowhere else yet which do not feed 

 upon them, like certain anemones. Many small fishes and 

 other creatures live among their branches, protected from their 

 enemies by their stinging tentacles, while a wealth of different 

 types, especially worms and molluscs, hide themselves away 

 in the stony bases of the large corals. 



A group of colonial coelenterates, the so-called siphonophores, 

 including the Portuguese man-of-war, one of the most formid- 

 able of all the jelly-fishes on account of its unusually developed 

 stinging powers, and a group of colonial tunicates have adopted 

 an oceanic life and all the species drift about as true elements 

 of the oceanic fauna. 



Besides these colonial attached animals there are many 

 others which live attached, but never form colonies, though 

 many are highly social. 



The most familiar of these are, perhaps, the barnacles, some 

 of which, like acorn barnacles, live closely appressed to rocks, 

 piles, the carapaces of sea-turtles, etc., while others, like the 

 goose barnacles, formerly supposed to be the young of the 

 barnacle goose, are stalked and are most frequently seen on 

 floating bits of wood and on the bottom of ships. The bar- 

 nacles have several pairs of curved feathery appendages with 



