86 INVERTEBRATE ANIMALS. 
“umbrella” (fig. 29), from the roof of which is suspended a 
single polypite, the lips of which are extended irito lobed pro- 
cesses, often extending far below the margin of the disc. The 
digestive cavity of the polypite gives out from its upper 
extremity a series of radiating gastro-vascular canals, which 
proceed towards the margin of the umbrella. These radiating 
canals are never less than eight in number, and on their way to 
the margin of the disc they break up into a great number of 
smaller vessels, which unite with one another to form a compli- 
cated net-work. At the margin of the bell they all open into a 
Fig. 29.—Generative zodid of one of the Lucernarida (Chrysaora Aysoscetla). 
(After Gosse.) 
circular vessel, which in turn sends processes into a series of 
marginal tentacles, which are often of extraordinary length. Be- 
sides the tentacles, the margin of thé umbrella is provided with 
a number of marginal bodies, each of which consists of a little 
collection of pigment or “eye-speck,” and a little sac filled with 
fluid and containing mineral particles. Each of these marginal 
bodies is covered and concealed from view by a kind of hood 
derived from the ectoderm. Hence the name of “hidden- 
