XI TRACHOMEDUSAE NARCOMEDUSAE 295 



Fam. Geryoniidae. — In this family there are four or six 

 radial canals, tlie statorhabs are sunk in the mesogloea, and a 

 tongue is present in the manubrium. Liriope (Fig. 137) is 

 sometimes as much as three inches in diameter. It has a very 

 long manubrium, and the tongue sometimes projects beyond the 

 mouth. There are four very long radial tentacles. It is found 

 in the Atlantic Ocean, the Mediterranean Sea, and the Pacific and 

 Indian Oceans. Geryonia has a wider geographical distribution 

 than Liriope, and is sometimes four inches in diameter. It differs 

 from Liriope in having six, or a multiple bf six, radial canals. 

 Carmarina of the Mediterranean and other seas becomes larger 

 even than Geryonia, from wliich it differs in the arrangement of 

 the centripetal canals. 



Liriantha appendiculata sometimes occurs on the south coast 

 of England during September, October, or at other times. 



Order VIII. Narcomedusae. 



The Narcomedusae differ from the Trachomedusae in having 

 the margin of the umbrella divided into a number of lobes, and 

 in bearing the gonads on the sub-umbrellar wall of the gastral 

 cavity instead of upon the radial canals. The tentacles are 

 situated at some little distance from the margin of the umbrella 

 at points on the aboral surface corresponding with the angles 

 between the umbrella lobes. Between the base of the tentacle 

 and the marginal angle there is a tract of modified epithelium 

 called the " peronium." The manubrium is usually short, and the 

 mouth leads into an expanded gastral chamber which is provided 

 with lobular diverticula reaching as far as the bases of the 

 tentacles. The marginal sense-organs are in the form, of un- 

 protected statorhabs. Very little is known concerning the life- 

 history of any of the Narcomedusae. In Cunodantha octonaria 

 the peculiar ciliated larva with two tentacles and a very long 

 proboscis soon develops two more tentacles and creeps into the 

 bell of the Anthomedusan Turritopsis, where, attached by its 

 tentacles, it lives a parasitic life. Before being converted into a 

 Medusa it gives rise by gemmation to a number of similar 

 individuals, all of which become, in time, Medusae. The parasitic 

 stage is often regarded as the representative of the hydrosome 

 stage reduced and adapted to the oceanic habit of the adult. 



