20 



HYDROZOA 



SlPHONOPHORA. 



(a) Physophora hydrostatica. Pneumatophore ; nectocalyces ; dactylozooids ; nutritive polyps 

 (hardly distinguishable) in the midst of dact. ; tentacles with lateral branches terminated by batteries 

 of thread cells. 



(V) Physalia with large pneumatophore and long tentacles. 



(c) Velella with diagonal crest on the pneumatophore. 



