HTDROZOA. 113 



seven definable families, whose characters may be 

 stated thus : — 



Order PHYSOPHOEID^. 



Family i. ApoLEMiADiE. 



Pneumatocyst small. Coenosarc filiform. 



Nectocalyces and hydrophyllia present ; the 

 latter united with the other appendages into 

 groups, arranged at distant intervals along the 

 coenosarc. 



Tentacula without lateral branches. 

 Family 2. Stephanomiadje. 



Pneumatocyst small. Coenosarc filiform. 



Nectocalyces and hydrophyllia present ; the 

 latter arranged with the other appendages in 

 continuous series. 



Tentacida with lateral branches, terminated 

 by sacculi. 



Family 3. PHYSOPHORiADiE. 



Pneumatocyst small. Coenosarc filiform, 

 but short, and dilated at its distal end. 



Nectocalyces present, occupying most of 

 the coenosarc below the pneumatophore. No 

 hydrophyllia. 



Tentacula with branches and involucrate 

 sacculi. 



Family 4. Athorybiad^. 



Pneumatocyst occupjdng almost the whole 

 of the globular coenosarc. 



Nectocalyces absent. Hydrophyllia. 



Tentacula with branches and involucrate 

 sacculi, each having two filaments and a 

 median lobe. 



