HYDUOZOA. t)3 



float ; tht'i-c iire no swimiuiug-bells ur coveriuir-pif -cs. Physalia 

 pela/ica (Model, Case 3) has one loiijr siout main a-ntacle and ''P 

 numerous lesser ones; Garavella* (Model, Case 8) has mimerouij 

 large tentacles. The fli)at is borne wholly above the surfa*;.-, and w 

 carried alon^^ by the breeze with the broad end foremost and the 

 teuLacles trailing behind. Prof. Agassi/, saw specimens with tentacles 

 over fifty feet in length. I'hysalia is notorious fur its dangerous 

 stinging properties.^ 



Rkodalia niiranda* is a deep-sea Siplujiiophoran, woiidi-rfully 

 adapted for living at great depths ; the depressed oval air-sac i« 

 followed by several circles of swimming-bells eiich attache<l by a 

 broad vertical lamella to the stem. 



A curiously modified swimming-bell, the aurophore, allows of 

 communication between the air-sac and the water ; by emptying or 

 secreting the air or gas the aiiimil can sink or rise within certain 

 limits without using its swimming-bells. The " stem " is not a 

 delicate tubular siphon as in Phi/sopkoni, but forms a thick raiuss 

 permeated by canals, the feeding poly[)s with tentacles and irenerative 

 buds being attached to its lower siu'face. 



^lost of the swimming-bells and all the tentacles have become 

 detached in the specimen, the red colour of which is artificial ; 

 but the air-sac and massive stem are well preserved. The specimens 

 were obtained by the Ghallenger from a depth of (iou fathoms in 

 the South Atlantic. 



Diplitjes * (Fig. 21 a, li), which is without an air-sac, lias two Cajie :\. 

 swimming-bells, and below these groups of covering-pieces, feeding ^"^ ^'^'^' 

 polyps, and generative buds situated along the stem. 



In Velella* or " By-the-wind Sailer " (Case 3), a vertical semi- 

 circular "sail "is attached diagonally across the upper surface of 

 an oblong disk : attached to the lower surface of the latter are one 

 large central feeding polyp and circles of smaller feeding polyps, 

 generative buds, and a marginal fringe of tentacles. Fleets of 

 Velella sailing along in the breeze are more commonly seen in 

 warm latitudes, but specimens, b!)th of I'rlflla and PlujsnUa, have 

 been found off the soulli-west coasts of England. 



Poi-jil'a * consists only of a circidar ilisk with its (le[>endent polyps 

 and tentacles. 



' Mrs. David mentions in her book on Funafuti that the natives aro more 

 afraid of Phijsalia than they are of the sharks. 



