248 



Pn 



provisional appendages 

 is formed which allows 

 us to regard the develop- 

 ment of the >S i phono- 

 pliora as a metamorphosis 

 (fig. 188 and 189). 



The crown of hydro- 

 phyllia, which is com- 

 pleted by the addition of 

 fresh hydrophyllia after 

 the appearance of a 

 tentacle with provisional 

 groups of neraatocysts, 

 persists only in Athory- 

 bia, where a swimming 

 column with nectocalyces 

 is never foimed. 



In Agalmop&is and 

 Physophora the primary 

 hydrophyllia of the larva 

 fall off' as the stem be- 

 comes larger, and are 

 replaced by nectocalyces. 



(1) Sub-order: Physor 

 phoridw. Stem short, 

 extended in the form 

 of a sac (fig. 190), or 

 elongated spirally (fig. 

 191), with a pneumato- 

 phore, usually nectocaly- 

 ces, which are arranged 

 in two or more rows on a 

 swimming column below 

 the piieumatophore. 

 Hydrophyllia and dacty- 

 lozooids are usually 

 present, and alternate 

 with the polyps and 

 gonophores in regular 

 order. The body of the 

 larva usually develops 



FIG. Wl.Haliftemmatergeftmum. Pn, pneumatophore 

 S. Nectocalyx ; f, polyp ; D, hyclrophyllium ; JV7-, groups of neraatocysts 



