HYDROIDS. 



79 



Pacific, and waited long for the expansion of the animals, but 

 was never gratified by their making their appearance. Agassiz 

 observes that they are very slow in expanding themselves. 

 When expanded, they have no resemblance to true polyps. 

 There is simply a fleshy tube with a mouth at top and a few 

 small rounded prominences in place of tentacles, four of 



KILLEPORA ALCICORNIS. 



them sometimes largest. The next figure, from Agassiz, 

 shows, much enlarged, a portion of a branch ot the Millepora 

 alcicoiiiis with the animals expanded, and the small figure <?, 

 near the top of the cut, gives the natural size of the same. 



The corals of the Milleporae are solid and stony, as much 

 so as any. in coral seas. They have generally a smooth 



