60 
GUIDE TO THE CORAL GALLERY. 
Case 3, almost microscopic suctorial mouths armed with fine tentacles 
Upright part, 24 c) are abundant in the cauliflower-like regions of the arms. 
Very commonly small fish are found associated with the larger 
Medusae, which doubtless shelter their proteges and enable them to 
dodge out of the way of their enemies. The majority of known 
Medusae do not live at any great depth, but a few forms inhabit 
the deeper zones of the ocean. 
Fig. 23. 
Pilema, a Rhizostome Medusa, a, entire animal (diminished), b, vertical section, 
c, one of the suctorial mouths, c, arm canal; gf, gastral filaments; gon, eggs; 
or. a, oral arms ; rad.c , radial canals ; s.mth , suctorial mouths ; st, stomach ; t 1, t 2, t 3. 
tentacles on oral arms. (After Cuvier, Claus and Huxley; from Parker and Haswell’s 
Zoology.) 
SlPHONOPHORA. 
The members of this group are free-swimming colonial Hydrozoa, 
in which the individuals composing the colony are modified in 
various ways according to the work they perform. 
Case 3 Physophora (Fig. 24c), for example (see Models and speci- 
Upright part, men in Case 3), a hollow stem or siphon is provided at its upper 
end with a small air-sac, below which follows series of swimming- 
