THE CCELENTERATA 57 



Nor is this all. The original embryo that has settled on 

 the rock may, instead of giving rise to a pile of discs, only 

 grow to a form resembling a little anemone with long 

 slender tentacles, then throw out threads from the sides of 

 its base, which cling to the rock and give rise, at intervals 

 of its length, to fresh buds, which develop to the anemone 

 form like young strawberry plants on their " runners "- 

 until a vast colony is formed, looking like a patch of white 

 velvet on the rock surface. Then some, or all, of the 

 individuals may take on the process of strobilation, develop 

 into piles of discs, and set free Ephyrm in vast numbers, so 

 that an immense number of individuals results from one 

 single egg. 



This tremendous method of reproduction accounts for 

 those sometimes mysterious appearances of jelly-fishes in 

 swarms which make the sea look alive with them. 



The adults pass a brief, but in the way of reproduction 

 active, existence, and the process is renewed. 



Unfavourable circumstances alone keep this multiplica- 

 tion in check, for, as far as is known, nothing preys on the 

 jelly-fishes. 



A pretty form, with the disc in radiating segments of pale 

 copper colour and pearly- white, which also sometimes 

 swarms on our coast is Chrysaora (see Fig. 21). It has 

 streamers around the mouth margin sometimes nearly a 

 foot in length, and these are pearly white and beautifully 

 frilled. It also has twenty-four long and slender tentacles 

 hanging from the margins of its disc. 



The jelly-fishes are all plentifully armed with sting 

 cells, and all (except Rhizostoma, which has a modified and 

 almost suppressed mouth arrangement) are predaceous 

 and voracious. 



It may have been noticed by the reader that many jelly- 

 fishes give shelter within their " pockets " to other 

 animals for instance, the great Rhizostoma usually has 



