246 



CGELENTEEATA. 



The second form of appendage, the gonopJiores, usually possess a 

 bell-shaped mantle containing circular and radial vessels, and surround- 

 ing the central stalk or clapper (manubrium), which is filled with 

 ova or spermatozoa. They usually arise in clusters at the base of the 

 tentacles, more rarely from the nutritive Polyps themselves (e.g. in 

 Velella). The male and female generative products always arise 

 separately in differently shaped buds, but are usually found closely 



approximated on the scnn 

 stock (fig. 186). There are, 

 however, also dioecious Sipho- 

 nophora, or if the medusoid 

 buds or gonophores be regarded 

 as generative organs, Sipliono- 

 phora of distinct sexes, e.g., 

 ApolemicL uvaria and Diphyes 

 acuminata. The ripe sexual 

 Medusoids frequently become 

 separated from the stock, i.s. 

 after the development of the 

 generative products, and only 

 rarely become liberated as 

 small Medusce (Chrysomitra in 

 the Velellidce), which produce 

 generative products during 

 their free life. 



Besides the constant nutri- 

 tive Polyps and medusoid 

 gonophores, there are incon- 

 stant appendages, which are 

 also modified Polypoids or 

 Medusoids. These are the 

 mouthless worm-like dactylo- 

 zoids (fig. 186), which, like 

 the Polyps, are provided with 

 a tentacle, which is, however, 

 shorter and simpler, and has no lateral branches or aggregations 

 of nematocysts ; also the leaf -shaped hard cartilaginous hydropJiyllia, 

 which serve to protect the polyps, dactylozoids, a-nd gonophores ; and 

 finally the appendages known as nectocalyces, which are placed beneath 

 the pneumatophore. The nectocalyces have a structure similar to 

 that of the Medusse, though their bilateral symmetry is apparent ; 



NK 



FIG. 189. Small larval stock of Agalmopsis after 

 the type of Athorylia. Lf, Pneumatophore ; 

 D, hydrophyllium ; Nk, groups of nemato- 

 cysts ; P, polyp. 



