CORY.MORPHA NUTANS. 209 



bands. Under a low magnifying power these bands are found to inosculate with one another 

 here and there, while towards the base of the stem they become fewer and broader by coalescence. 

 They represent canals excavated in the endoderm of the stem, and in a transverse section of tlie 

 stem (fig. 5) these canals may be seen to lie just within the ectoderm. The peripheral portion 

 (d) of the endodeiiu in which they are excavated is composed of small spherical ceils filled with 

 reddish granules, which give to the stem its pale reddish tinge, while the whole of the axis (e) of 

 the stem is occupied by a sort of pith, composed of large cells with colourless contents. Very 

 distinct currents may occasionally, by means of the microscope, be witnessed in the canals, so 

 that the structure and phenomena presented by these parts closely correspond to what we meet 

 with in the stems of Tabiilarla iiuKvim. 



Under a high power of the microscope delicate parallel longitudinal strioe may be detected 

 lying external to the canals. They may be traced upwards for some distance on the body of the 

 hydranth. They lie between the endoderm and ectoderm, and represent a fibrillated muscular 

 tissue. 



The peculiar short conical papillae (fig. 1, a) which arc given off from the stem near its proximal 

 end are arranged in regular longitudinal series, which follow the course of the canals, the stem 

 immediately over each canal bearing two alternate rows. They are tubular, with the cavity of the 

 tube apparently communicating with the canal over which they lie, and witii their free extremities 

 blunt and imperforate (figs. 10, 11). They appear to be extensile, and one or more of them n)ay 

 occasionally be seen to be much elongated, and then with their extremities slightly clavate 

 (fig. 10). 



These tubular processes have never been seen to act as organs of adhesion, nor have we yet 

 any evidence of the office they may serve in the economy of the animal, but it is impossible not 

 to recognise in them structures having a close relation to the filaments of attachment which are 

 given off from the stem a little lower down. 



These filaments (fig. \,b,b) constitute a remarkable feature in the structure of the Corymorpim. 

 When the hydroid is examined shortly after its detachment from the sea-bottom no trace of them 

 may be discoverable ; but after resting for a few hours in our aquaria the filaments become developed 

 in great numbers from the whole of that part of the stem which lies below the papilliform pro- 

 cesses, passing outwards through the fine structureless pellicle which here loosely invests the 

 extremity of the stem. They now rapidly extend themselves, adhering closely to the sides of the 

 aquarium and by repeatedly crossing one another form an entangled web-like tissue, by which the 

 Corymorpha has become attached. It is almost certain that such filaments existed also before 

 the removal of the hydroid from its native bed, but that in the act of detachment they were torn 

 off. to be renewed when an opportunity may be afforded, as in the confinement of the aquarium. 



Under the microscope the filaments are found to be tubular, terminating each in an imper- 

 forate clavate extremity. They consist of a granular substance, which, as it continues to elongate 

 itself, becomes invested with a perfectly transparent, structureless film of extreme tenuity. 



Besides these capillary filaments of adhesion there is nothing which can be regarded as a 

 hydrorhiza, and it would seem that the chief support of the hydroid, when in its natural condition, 

 is afforded by the proximal end of the hydrocaulus, which is then plunged into the sand of the 

 sea-bed, and thus fixes the hydroid to its place. 



The Hydranth. — The hydranth (fig. 1) may be described as flask-shaped. It bears, towards 

 its base, a zone of long, imperfectly contractile tentacles, arranged in a single series, while at a 



