20 



BRANCH CtELKNTEUATA 



pillar-like looping it is able to change its position or perform 

 slight locomotion. 



Dispersal. While the mature Hydra has veiy limited powers 

 of locomotion, or direct dispersal, its offspring may be widely 



Fig. 11. A, Part of the colony of Bougainvil'lea mus'cus, one of the com- 

 pound Hydrozoa, of the natural size. B, Part of the same enlarged: p, A 

 polypite fully expanded; ra, an incompletely developed reproductive bud; 

 m', a more completely developed reproductive bud; /, ccenosarc with its 

 investing periderm and central canal. C, A free reproductive bud or medu- 

 siform gonophore of the same: n, Gonocalyx; p, manubrium; c, one of the 

 radiating gastrovascular canals; o, ocellus; v, velum; t, tentacle. (After 

 Allman.) 



separated from the parent through indirect dispersal, or the 

 drifting about of the encysted eggs by means of currents and 



