NATURE ADRIFT 



The big jellyfish spawn in the autunin before being killed off during the 

 winter and the young larvae settle on rocks and stones, especially near the 

 coasts, where they remain attached as elongated blobs of jelly called 

 'scy phi stoma (Plate XIII). In the spring each divides like a pile of saucers, each 

 saucer splitting off, turning upside down and swimming away as an 'ephyra' 

 which grows into a new jellyfish. Not until the summer, however, when they 

 have grown big are they generally noticed. A big outbreak, such as occurred 

 in 1959, is thus the result of a good brood of young ones followed by con- 

 ditions that enable more than usual to survive. Although this would produce a 

 lot of eggs, the crop the following year would depend much more on the 

 winter conditions and the plankton available as food during the following 

 spring and summer. 



Another large jellyfish that is native to the waters round the British Isles, 

 and north-east Atlantic coasts generally, is the cauliflower jelly, Rhizostoma 

 octopus (Fig. 16; 4). This, too, can reach a yard across. The upper side of the 

 umbrella is a rather dirty white in colour and unmarked except for a bright 

 purple fringe round the edge, and below it are four large holes leading to the 

 reproductive organs. Hanging down is the 'cauliflower' part which is the 

 stomach branched and rebranched until it ends in thousands of mouths — the 

 name Rliizostoiim means root like mouths — which filter off the plankton on 

 which it feeds. It therefore does not need to paralyse its prey and in spite of 

 its formidable look it is not a stinger. The 'cauliflower' ends in eight distinct 

 arms and hence the specific name 'octopus'. 



Chrysaora (Fig. 16; 2) is another large jellyfish which, although not so 

 common as Amelia or Cyaiiea is often stranded on our shores (Plate XII). It 

 can be recognized by its chocolate-coloured wedge-shaped markings. The 

 pearl jelly Pelagia, Fig. 16; i, is an Atlantic form sometimes brought in by the 

 ocean currents in quite large numbers. 



Another 'Order' of Coclenterata occurring in the plankton is the Siphon- 

 ophora, a wholly planktonic group. They are colonial forms, i.e. each is a 

 colony of a number of individuals each with its own job to do, the whole 

 acting as one animal. Some are simple transparent bells, or double bells with 

 only small trailing tentacles (Fig. 17; i). Others are more complicated, some 

 of the individuals acting as floats, some as swimming bells, others as 

 food catchers and yet others solely engaged in reproduction (Fig. 17; 2 and 3). 

 Like the stinging jellyfish, they catch and paralyse their prey with trailing 

 tentacles armed with stinging cells. 



Although most of them are so delicate that -they are diflicult to capture 

 whole and are quite harmless to us, one of them — Physalia, the Portuguese 

 Man o' War — is a really nasty creature in spite of its pleasant colours (Fig. 

 17; 4: Plate II). Found in most of the warmer waters of the North 



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