422 Rev. T. Hincks on a new Genus of Hydroida. 



These organs are capable of great elongation and contraction, 

 and execute the most vigorous movements, stretching themselves 

 out with apparent eagerness, and twisting in all directions. My 

 attention -was first drawn to the zoophyte by a number of them, 

 disposed on the creeping stolon, which were in a state of most 

 lively excitement, and manifesting a large amount of muscular 

 energy. 



One of these organs is almost always attached to the hydro- 

 caulus a little below the calycle, and when in a state of exten- 

 sion it rises above it ; and as it twists itself about, with its for- 

 midable armature ready for instant action, it has all the appear- 

 ance of a purveyor to the polypite. Many of them are also 

 distributed upon the hydrorhiza. 



A striking feature of the genus Ophiodes is the constriction 

 of the body of the polypite, dividing it into two well-marked 

 regions — the oral, including the mouth and the tentacular 

 circle and a kind of quasi pharynx, and the ahoral, traversed by 

 the digestive cavity. 



The polypite does not extend to the bottom of the hydrotheca, 

 but rests on a membranous diaphragm that shuts off the upper 

 third of it and forms a cup-shaped chamber. This diaphragm 

 is perforated in the centre, and through the orifice the body is 

 linked on to the coenosarc, that traverses the lower portion of 

 the calycle. 



0. mirabilis, n. sp. 



Hydrocaulus erect, slightly branched, rudely annulated at the 

 base, and jointed at intervals throughout. Hydrotheca in the 

 form of a vase, bulging slightly immediately above the base ; 

 the sides incurved, expanding gradually towards the top, with 

 an everted rim ; a single tentaculoid organ on the stem a little 

 below the calycle, and many distributed on the stolon ; polypites 

 tall, the inferior portion of the body clavate, the oral funnel- 

 shaped; tentacles about fifteen, a brownish cluster of thread- 

 cells between each pair on the connecting web. Reproductive 

 organs unknown. 



Height about y ^ of an inch. 



The branching of the Ophiodes mirabilis, as I have seen it, is 

 of the simplest kind, usually consisting of a single division of 

 the stem. It may possibly attain a more luxuriant growth; but 

 I have examined a considerable number of specimens, and have 

 always found it to be either simple or furnished with one or two 

 short branches. 



The polypite, when fully extended, is a singularly beautiful 

 object, imitating to some extent the form of a tall and graceful 

 candelabrum. Only the base of the body is within the calycle. 



