mackerel. A Japanese observer has seen Nomeiis 

 nibbling on the tentacles of its host, and perhaps it is 

 in this way that it develops immunity to the stings. 

 Whether Nomeus lures bigger fishes to the tentacles, 

 as some say, we do not really know, but Physalia 

 does feed on fishes — some accounts say mainly on 

 flying fishes. This is not hard for us to believe, as our 

 own first experience of Physalia was in the Carib- 

 bean, where for some eight or nine sunny hours our 

 ship sailed through water seemingly alive with flying 

 fishes and dotted to the horizon with a great flotilla of 

 Physalia. Even from the deck of the small ship one 

 could see the crest changing its shape and the float 

 dipping from side to side in the quiet air. Douglas 

 Wilson, who has studied physalias that occasionally 

 come to Plymouth, in England, has suggested that 

 this habit serves to keep the delicate float wet in hot, 

 calm weather. A physalia kept in an aquarium will 

 eat a preferred fish, first stinging and entangling it in 

 the tentacles and then hauling it up under the float. 

 There feeding polyps stretch down to spread their 

 thin, transparent lips until they overlap, completely 

 enveloping the fish as they pour out digestive juices 

 and dissolve the flesh. The food particles are drawn 

 up into the colony, further digested, and shared. 

 Physalias fall prey to petrels and albatrosses, and 

 fishes too, if we believe one old account that tells of 

 an albacore swallowing a physalia and its accom- 

 panying little fishes. On tropical beaches ghost crabs 

 nibble at stranded physalias from below, thus help- 

 fully burying them. 



The common jellyfish of all seas. Aiirelia atirita. Here 

 the saucer-hke umbrella is seen from below. ( Eng- 

 land. D. P. Wilson) 



Vivid accounts of pelagic invertebrates, including 

 Physalia, are to be found in D. P. Wilson's Life of 

 the Shore and Shallow Sea and in Hardy's The Open 

 Sea. The only place known to us where living sipho- 

 nophores have been regularly displayed to the public 

 is the Naples Aquarium. In the past, at least, Phy- 

 sophora. Forskalia, and Hippopodiiis were shown in 

 the tanks whenever quiet weather made them avail- 

 able. Sea anemones, sea pens, and other sessile coe- 

 lenterates are on display in many seaside public 

 aquariums. 



The True Jellyfishes 



( Class Scyphozoa ) 



Almost all of the larger jellyfishes one sees in ma- 

 rine waters or washed up on the beaches as shapeless 

 blobs of jelly are true or scyphozoan jellyfishes. 

 Most familiar of these is the moon jelly, Aiirelia, 

 which can be seen in great shoals from the deck of an 

 ocean liner. The milky saucers drift along together 

 or swim slowly by rhythmic pulsations. The giant 

 among jellyfishes is Cyanea arctica, sometimes 8 

 feet across, with long, trailing tentacles that extend 

 downward for 200 feet. In the cold waters where 

 these occur no swimmer could last long anyway, so 

 we can only imagine what it would be like to be stung 

 by such a monstrous coelenterate. Of more real con- 

 cern are the 12-inch Cyaneas of temperate Atlantic 

 waters, for these do turn up off beaches in summer, 

 and they can cause painful red welts that remain dis- 

 colored for many hours. Since some people also de- 

 velop generalized symptoms or disabling muscular 

 cramps, any swimmer stung by a jellyfish should 

 promptly go ashore. There seems to be disagreement 

 over whether there are any fatalities known to be 

 due solely to Cyanea poisoning or to the painful 

 stings of Dactylonietra qiiinqiiecirrha. both common 

 in the Atlantic. In tropical waters scyphozoan jelly- 

 fishes can be more dangerous. A sea wasp, Chiro- 

 psalmiis quadrigatus, of the South Pacific and Indian 

 oceans, is said to have caused deaths in from three to 

 eight minutes. Such reports do not always rule out 

 death from other possible causes, but the bad reputa- 

 tion of this cuboidal jellyfish is probably deserved. A 

 swimmer or diver who feels uncertain about a mass 

 of jelly coming his way should give it plenty of lee- 

 way, remembering that it is probably trailing long 

 tentacles for some distance. 



After a great storm, tropical waters or even beach 

 sands may be filled with tentacle fragments still cap- 

 able of dealing painful stings. Any jellyfish stranded 

 at ebb tide should be examined with a stick or turned 

 over with the toe of one's shoe, but not touched with 

 bare skin unless readily recognized as of a harmless 

 species. Having set down all these warnings, it is 

 only fair to point out that of the two hundred or so 



