NARCOMEDUSAE 121 



margin ; tentacles stiff and extending from the exurabrella ; gonads on the 

 subumbrella ; gastrovascular cavity a wide central space, either circular 

 in outline or with radial pouches or canals extending outwards; ring 

 canal follows the marginal lobes but is often absent; lithocysts free 

 and often projecting, with entodermal concretions; a thickened ecto- 

 dermal ring is at the edge of the umbrella with prolongations called 

 peronia extending to the base of the tentacles, and often others also, 

 called otoporpae, extending upwards from the base of the lithocysts: 

 2 families and 50 species, of which a few are found along our coast. 



FAMILY ^EGINIDAE. 



Radial pouches of gastrovascular space present : 11 genera. 



1. CUNOCTANTHA Haeckel. Tentacles, marginal lobes, and radial 

 pouches 8; otoporpae present; the larvae live parasitically in the bell 

 of the mother or some other medusa where they bud off new larvae from 

 a stolon-like prolongation of the apical 



end of the umbrella: 5 species. 



0. octonaria McCrady (Fig. 203). 

 Diameter 7 mm. ; manubrium cone-shaped 

 with 4 lips: common at Beaufort, North 

 Carolina, the larvae infesting Turritopsis 

 nutricula; cosmopolitan. 



2. CTJNINA Eschscholtz. Tentacles 



and radial canals 9 to 24; the larvae live parasitically in the bell of the 

 mother or some other medusa : 10 species. 



C. lativentris Gegenbaur. Medusa flat, transparent, about 16 mm. in 

 diameter; tentacles, marginal lobes, and stomach pouches 10 to 12; litho- 

 cysts on each lobe 4: Atlantic Ocean and Mediterranean Sea. 



Order 7. SIPHONOPHORA.* 



Free-swimming, colonial Hydromedusae. The individuals forming a 

 colony are in a high degree polymorphic, there being several orders of 

 individuals all of which are in communication with one another by means 

 of the common gastrovascular space. Each order performs a distinct 

 function in the colony, the division of labor being similar to that which 

 obtains among the various organs of the body of one of the higher 'animals. 

 Two general types of structure are met with among the SiphonopJiora. In 

 one (Fig. 204) the various individuals bud off from a long axial tube, 



* See "The Siphonophorae of the Challenger," by E. Haeckel, Challenger 

 Reports, Vol. 28, 1888. 



