JELLY-FISHES. 809 



but it is seldom that we see them thus straightened ; for 

 they are ever assuming the most elegant spiral coils, which 

 open and close, extend and contract, with an ever chang- 

 ing vivacity. The animal has a very perfect control over 

 each thread, as well as over each individual secondary 

 filament. They are, either together or separately, fre- 

 quently projected from their chambers to their full extent 

 by one impulse ; sometimes the extension is arrested at 

 any stage, and then proceeded with, or the thread is par- 

 tially or entirely retracted. Sometimes the secondary fila- 

 ments are coiled up into minute balls, scarcely perceptible, 

 or only so as to give to the main thread the appearance of 

 small beads remotely strung on a fine hair ; then a few 

 uncoil and spread divergently ; contract again, and again 

 unfold; or many, or all, interchange these actions toge- 

 ther, with beautiful regularity and uniformity, repeating 

 the alternation for many times in rapid succession. 



The beauty and diversity of the forms assumed by these 

 elegant organs beguile us to watch them with unwearied 

 interest, and we wonder what is their function. For, with 

 all our watching, this is by no means clear. They are 

 certainly not organs of motion. At times it seems as if 

 they were cables intended to moor the animal, while it 

 floats at a given depth ; for we see them with their ex- 

 tremities spread upon the bottom, to which they appear 

 to have a power of adhering, thus forming fixed points, 

 from which the little globe rises and falls at pleasure, 

 shortening or lengthening its delicate and novel cables, 

 maintaining all the while its erect position. 



When the Cydippe swims, however, which it does with 

 great energy, the threads seem unemployed, streaming 

 loosely behind, and evidently taking no part in the pro- 

 gression, though still adding beauty and grace to the tout 

 ensemble. The organs by which the sprightly motions of 

 the whole animal are effected are of quite another charac- 

 ter, and shall now engage our attention. 



