20 



BRANCH CCELENTERATA 



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

 slight locomotion. 



Dispersal. — ^While the mature Hydra has very limited powers 

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



Fig. 11. — A, Part of the colony of BougaiiivU'lea iiuis'cua, one of the com- 

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

 polypitc fully expanded; m, an incompletely developed reproductive bud; 

 m', a more completely developed reproductive bud; /, coenosare 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 

 AUman.) 



separated from the parent through indirect dispersal, or the 

 drifting about of the encysted eggs by means of currents and 



