60 



GUIDE TO THE COKAL GALLERY. 



Case 3, almost microscopic suctorial mouths armed with fine tentacles 

 Upright part. ^pjg_ 24c) are abundant in the cauliflower-like regions of the arms. 

 Very commonly small fish are found associated with the larger 

 Medusa, which doubtless shelter their proteges and enable them to 

 dodge out of the way of their enemies. The majority of known 

 Medusa do not live at any great depth, but a few forms inhabit 

 the deeper zones of the ocean. 



Fig. 23. 



TCtd.C 



s.rntlL 



I'ilema, a Rhizostome Medusa, a, entiie animal (diminished), b, vertical section, 

 c, one of the suctorial moutlis. c, arm canal; gf, gastral filaments; gon, eggs; 

 or.«,oral arms; rad.c, radial canals ; s.mih, suctorial mouths; st, stomach ; < 1, < 2, < 3, 

 tentacles on oral arms. (After Cuvier, Clans and Huxley ; from Parker and Haswell's 

 Zoology.) 



SiPHONOPHORA. 



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. 



Q^gg 3 In 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- 



