HABITS OF LUCEKNARIA. 169 



state of expansion, they are sufficiently conspicuous 

 from the beauty and singularity of form, but when 

 contracted they are easily overlooked. They feed on 

 small crustaceous animals brought within their reach 

 by the tide or their own destiny, and, to arrest these 

 more certainly, the tentacula are widely displayed ; 

 but no sooner do they feel their prey, than they in- 

 stantly contract, envelope it in their joint embrace, 

 and carry it to the mouth by an involution of the 

 whole marginal circumference. 



Their mode of progression, as we learn from 

 Mr. E. Q. Couch, differs under different circumstances. 

 If intending to move to any great distance, they do so 

 by loosening their attachments, and then by various 

 and active contortions they waft themselves away till 

 they meet with some obstruction, where they rest, 

 and if the situation suits them, they fix themselves ; 

 if not, they move on in the same manner to some 

 other spot. If the journey be only for a short di- 

 stance, as from one part of the leaf to another, they 

 bend their bell-shaped rims, and bringing their tenta- 

 cula in contact with the fucus, adhere to it by their 

 assistance. The footstalk is then loosened, thrown 

 forward, and twirled about till it meets with a place 

 to suit it ; it is then fixed, and the tentacula are dis- 

 engaged ; so that in this way the polyps move from 

 one spot to another. Sometimes they walk about like 

 the Actiniae by a gliding movement of the stalk. 



In taking their prey they remain fixed, with their 

 tentacula expanded; and if any minute substance 

 comes in contact with one of the tufts, that tuft con- 

 tracts and is turned to the mouth, while the others 

 remain expanded, watching for food. 



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