SYNOPSES OF NORTH-AMERICAN 
INVERTEBRATES. 
AIV. Tue HypROMEDUS& — Part III. 
CHARLES W. HARGITT. 
MEDUS&. 
THE Medusze (medusoids, medusiform persons, gonophores, 
Sonozooids) of this class of ccelenterates may be designated 
as in general of the form of a more or less transparent bell, or 
saucer-shaped disk, varying in size from the almost microscopic 
to organisms of fifteen inches or more in diameter. 
The comparison of the medusa with a bell is fairly good, its 
body being similar in form in typical cases to the body of the 
. bell, the manubrium corresponding to the clapper. A similar 
comparison with an umbrella is almost equally appropriate, if 
not superior. In this case the body of the medusa would cor- 
respond to the extended disk of the umbrella, the manubrium 
to the handle, and in some respects the radial canals are 
comparable with the ribs of the umbrella, while the numerous 
tentacles of some Species are somewhat comparable with the 
marginal fringe often seen upon a lady's parasol. In further 
keeping with this comparison the outer, aboral portion of the 
medusa bell has been designated as the exumbrella, the inner, 
concave portion of the bell as the subumbrella. The mouth is 
located at the terminal, pendent portion of the manubrium, and 
through the tubular canal as an cesophagus communicates with 
the gastric pouch or stomach, from which radiate the gastric or 
chymiferous canals, by means of which the digested food matter 
is distributed over the body and through the circular or cir- 
cumferential canal to the marginal organs. 
At first sight there might seem to be little in common 
between the medusa and hydranth, either as to form, structure, 
575 
