HTDRO/OA SIPHOXOPI IORA . 



243 



Order 2. SIPHONOPHORA.* 



Free-sa-i nit/tiny polymorphous hydroid-stocks with contractile stem, 

 with polypoid 

 nutritive indi- 

 viduals and 

 medusoid buds, 

 usually also 

 with nectocaly- 

 ces, hyrophyllia 

 and dactylo- 

 zooids. 



Morphologi- 

 cally the Sipho- 

 nophora are 

 directly allied 

 to the hy- 

 droid-stocks ; 

 but they possess 

 to a much 

 greater extent 

 than the latter 

 the characters 

 of individuals, 

 in consequence 

 of the highly 

 developed poly- 

 morphism o f 

 their polypoid 

 and medusoid 

 appendages. 

 The functions 

 of the latter 

 seem so inti- 

 mately con- 

 nected and are 

 so essential for 

 the preserva- 

 tion of the entire colony that we may regard each colony of Sipho- 



FIG. 185. Diagram of a colony of Phyaofilim-iii". St, Stem; Ek, 

 ectoderm ; En, entoderm ; Pn, Pneumatophor ; Sic, iiectocalyx 

 being budded off ; S, nectocalyx ; Z>, hydrophyllium ; G, gono- 

 phore ; T, dactylozooid ; Sf, tentacle ; P, polyp ; O, mouth of the 

 latter ; Nk, battery of nematocysts. 



' Besides Kolliker, C. Vogt. Huxley and others, compare C. Gegenbaur. 

 " Beobachtungen iiber Siphonoiihoren," Z< -itxrlirift fiir w/.v.v. Znol., 1853. C. 



