LUCERNARIDA AND GRAPTOLITID#. . 87 
eyed” Meduse, applied to these forms, in contradistinction to 
the “ naked-eyed” A/eduse, in which the eye-specks are exposed 
to view. The reproductive organs are usually of some bright 
colour, and ‘form a conspicuous cross shining through the 
thickness of the disc.” 
From the above description it will be evident that there is a 
considerable resemblance between the so-called ‘“ hidden-eyed” 
Medusa, or the reproductive zodids of many of the Lucernarida, 
and the medusiform gonophores of so many of the Hydrozoa, 
as well as the true Discophora or naked-eyed Meduse. The 
differences, however, between them are these : The swimming- 
Fig. 30.—Generative zodid of Rhézostoma (after Owen). @ Umbrella; 4 6 Tree- 
like peduncle covered with minute polypites ; ¢ c Anastomosing network of gas- 
tro-vascular canals. 
disc of the naked-eyed Meduse@ and of any medusiform gono- 
phore is furnished at its mouth with an internal shelf or veil ; 
the radiating gastro-vascular canals are very rarely more 
than four in number, and should they subdivide (as in rare 
cases they do), they do not form an intricate network ; lastly, 
the marginal bodies are simply placed in an uncovered 
