352 THE INHABITANTS OF THE SEA. 
Though generally preferring to lie at anchor, the Lucer- 
nariz are able to detach themselves, and to swim in an 
inverted position by the 
slowly repeated movements 
of their cup-like umbrella. 
When in a state of expan- 
sion, few marine creatures 
exceed them in beauty and 
singularity of fourm; when 
Poe contracted, they are shape- 
less, and easily overlooked. 
“(heir mode of progression,” says Mr. Couch, “ differs under 
different cireumstances. 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 any obstruction, where they rest; andif the situation 
suits them, they fix themselves; if not, they move on in the 
same manner to some other spot. If the change be only for a 
short distance, as from one part of a leaf to another, they bend 
their campanulate rims, and bring the tentacula in contact with 
the jaws, and by them adhere to it. The foot-stalk is then 
loosened and thrown forward and twirled about till it meets 
with a place to suit it; it is then fixed, and the tentacula are 
loosened, and in this way they move from one spot to another. 
Sometimes they advance like the Actiniz, by a gliding motion 
of the stalk. In taking their prey, they remain fixed with their 
tentacula expanded, and if any minute substance comes in con- 
tact with any of the tufts, that tuft contracts, and is turned to 
the mouth, while the others remain expanded watching for prey.” 
The Calycophoride are distinguished by the cup-shaped 
swimming organs, which form the most prominent part of their 
body. Generally transparent like glass, their course upon 
distant inspection is only revealed by the bright tints of 
some of their appendages. In Diphyes, the type of the group, 
the two cups (vy, v”) fit into each other so as to form a 
more or less perfect close canal. The common stem of the 
numerous polyp colony freely glides up and down the chamber 
thus formed, into which it can be completely retracted, and 
along its sides are placed the several appendages of the compound 
creature, consisting chiefly of polypites (7), tentacles, and 
