Sponges 37 



As a result of its boring activities the 

 shells become open to inrushes of water 

 and subject to attack from whelks and 

 other enemies. Further, it compels the 

 oyster to so thicken the inside of its 

 shell as to spoil it for presentation to 

 the ultra-fastidious epicure. On oyster 

 farms where this sponge is abundant, the 

 oysters are grown in frames, which are 

 now and then raised and exposed to 

 showers of rain, an exposure fatal to the 

 sponge, but which does no harm to the 

 oyster, who is able to close down. 



In the tropics an allied sponge actually 

 eats into stony coral reef, giving the 

 outer surface of the smothered coral the 

 appearance of a vigorous, healthy growth, 

 alive with rose-tinted polyps. But all is 

 rotten within and it crumbles at a touch 

 from the yacht's keel. In some cases 

 this parasitic sponge raises a series of 

 spires several feet in height, resembling 

 miniature cathedral towers. 



