CCELENTERATA. 29 



Order I. OALTOOPHORSl 



Polypites united by a filiform and unbranched coenosarc ; tlie 

 proximal end modified into a somatocyst, and provided with one 

 or more nectocalyces. 



" Sets of appendages each consisting of a hydrophyllium, a 

 hydranth with its tentacle, and gonophores, which last bud from 

 the pedicle of the hydranth are developed at regular intervals 

 on the coenosarc, and the long chain trails behind as the animal 

 swims with a darting motion, caused by simultaneous rhythmical 

 contraction of its nectocalyces, through the water." [Huxley.'} 

 The distal set of these appendages, as they attain their full 

 development, " becomes detached as a free-swimming complex 

 Diphyzooid" In this condition they grow and alter their form, 

 until the gonophores which they develop " become detached, 

 increase in size, become modified in form, and are set free as a 

 third series of independent zooids." 



These animals are so transparent as only to be noticed at a 

 distance by their bright tints. 



Diphyidcs. Sphceronectidce. Hippopodiidce. 



Diphyes. Sphseronectes. Hippopodius. 



Abyla. Monophyes. Vogtia. 



Prayidce. 

 Praya. 



Order II. PHFSOPHOK.E. 



Polypites united by an unbranched, or very slightly branched, 

 filiform, globular, or disooidal coenosarc ; the proximal end modi- 

 fied into a pneumatophore, and sometimes provided with necto- 

 calyces. Mostly monoecious. 



The tentacles are either attached to the coenosarc, or singly to 

 a polypite ; they are forty inches long in Halistemma rubrum, 

 while the pneumatophore is only three or four lines in its largest 

 diameter. The pueumatophore, however, is generally of much 

 larger size, and in the Velellidae it is "converted into a sort of 

 hard inner shell, its cavity being subdivided by septa into nume- 

 rous chambers." 



The members of this order differ considerably among them- 

 selves, but they all agree in having a pneumutophore. 



