CORAL-MAKERS AND JELLY-FISH 97 



full-sized Aurelia. I have only once had the chance of 

 witnessing this beautiful sight, and that was many years 

 ago in a tank at the Zoological Gardens (they have no 

 such tanks now), where the polyp-like young (called 

 " Hydra tuba *') spontaneously put in an appearance, and 

 proceeded to break up into piles of little disks, which 

 separated and swam off as one watched them. The 

 French poet, Catulle Mendes, imagined a world where 

 the flowers flew about freely and the butterflies were 

 fixed to stalks. His fancy is to some degree realized 

 by the swimming away of the young jelly-fish from their 

 stalks. There are a host of very minute jelly-fish, 

 measuring when full grown only half an inch or less in 

 diameter. They originate as buds from small branching 

 polyps, one kind of which is common on oyster- shells, 

 and is called "the herring-bone coralline." The dried 

 skins of these coralline polyps (which are horny) are 

 often to be picked up with masses of seaweed on the 

 seashore after a storm. The little jelly-fish are the ripe 

 individuals of the polyps, and produce eggs and sperm 

 which grow to be polyp-trees. These, again, after 

 growing and branching as polyps, give rise to little 

 jelly-fish here and there on the tree, which in most 

 kinds (though not in all) break off and swim away 

 freely. 



