HYDROZOA. 



109 



power of alternately raising and depressing its 

 kydrophyllia, so as to render them agents of pro- 

 pulsion. 



Fig. 22 





• 



a 



Morphology of Physophoeid^ : — a , Athorybia rosacea; b, 

 Mysophora Philippii ; a, pneumatophore ; v, nectocalyx ; /, rudi- 

 mentary nectocalyx ; <fc hydrocysts ; *, polypite ; t, tentacles ; 

 V, hydrophyllia. (About the natural size.) 



