CCELENTEKATA 



6 9 



c? 



Order 3. Siphonophora 



The Siphonophora (Gr. aKpoov, a siphon, and cf>epo), to bear) 

 are free-swimming colonies of marine Hydrozoa. These col- 

 onies are extremely compli- 

 cated in structure, owing to 

 the fact that there is great 

 division of labor among the 

 different members compos- 

 ing it, and therefore a differ- 

 ence in form corresponding 

 to the difference in function. 

 The colonies appear to de- 

 velop from a medusa-like 

 individual, which produces a 

 large number of buds, either 

 on the subumbrella (Fig. 53), 

 or on the greatly elongated 

 manubrium (Fig. 54). As 

 many as seven different kinds 

 of individuals may be found, 

 but all do not generally occur 

 in one colony (Fig. 55). 

 There is often a float, a 

 modified medusa containing 

 a cavity filled with gas, which 

 keeps the colon}- afloat. Be- 

 low this there may be a 

 greater or less number of 

 swimming bells, medusa? 

 whose only function is the 

 propulsion of the colonv. 

 At various points there may FlG . - 3 . PhyS a lla . As it floats on the surface 



be expanded, leaflike indi- of the sea. cr, crest; /, polyp; pit, pneumato- 

 • j , , . , phore or float. (After Huxlev, from Parker and 



Vlduals, which serve as a Haswell's Manual.) 



protective covering to those 



beneath them. Other individuals have very much the appear- 

 ance of polyps without tentacles, and function as feeding organs. 

 Near them are generally others resembling long tentacles, which 



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