24 A NATURAL HISTORY OF THE SEAS 



often distressingly abundant in warm weather off our 

 coasts, may be taken as a typical example. In its early 

 stages it becomes attached to a rock at low tide and may 

 then be mistaken for a very small Sea Anemone. As it 

 increases in size, however, an extraordinary transformation 

 takes place. The creature develops a long series of con- 

 strictions throughout its length and it is later apparent 

 that the animal is not one but many individuals all circular 

 in shape with tentacles arranged round the circumference, 

 the whole piled one upon the other like a stack of dinner 

 plates. When fully developed these detach themselves 

 one after the other, each embarking on a career of its own 

 and progressing by means of those umbrella-like expansions 

 and contractions which every seaside visitor has observed. 



The commonest stinging form which is justly dreaded 

 by bathers is Chrysaora. 



The largest species found in our seas is Rhi^pstoma, 

 which may have a diameter of 2 ft. The fry of the horse 

 mackerel habitually shelter beneath its large flattened 

 umbrella, which protects them from the searching eyes of 

 sea birds, whilst the abundant stinging cells ward off 

 predacious species of their own order. 



The giant of the race is Cyanea — the Sea Blubber, which 

 reaches its maximum diameter of 8 ft. with tentacles 

 120 ft. long in the waters north of Cape Cod. It is likewise 

 a noxious jellyfish. Such a monster is, like the rest of its 

 clan, composed largely of sea-water, the actual organic 

 tissue in its composition comprising not more than five 

 per cent, of the entire bulk. 



The Ctenophores, or Sea-gooseberries, carry swimming 

 plates — combes of partly fused hair-like organs — that by 



