THE HYDROIDS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 99 



to be creeping. The clustered bydrorhizal tubes of these create the resemblance to 

 fascicling, but the structure is analogous rather to the rhizocaulom often exhibited by 

 Lafoea dumosa than to a truly fascicled stem. The rhizoid nature of this compound 

 stem is confirmed by another specimen (Aglaophenia dubia) from the same locality, 

 where the two lower branches, at least so they appear to the eye, turn out to be distinct 

 climbing colonies of H. longicauda. 



The largest of the colonies found by the Scotia is 1 1 cm. in height. The specific 

 characters agree with those given by Professor Nutting, but in our specimens the 

 hydrothecse appear to have undergone a greater degree of tilting forward than his 

 figures indicate, while the lateral teeth are more strongly developed. The aperture is 

 vertical and slightly constricted, with a sharp tooth projecting upwards and outwards 

 on either side. The intrathecal ridge is well marked, arising near the middle of the 



Fig. 11.- — Halicornaria longicauda. Hydrothecse showing variation in the length of 

 the median nematophore. x 110. 



adnate portion of the mesial nematophore and extending backwards at an angle of 45° 

 with the axis of the hydroclade. Its free edge is slightly reduplicated. The supracaly- 

 cine nematophores are short and stout, and when viewed from the front appear clearly 

 above the hydrotheca, although they do not reach the margin of the aperture. The 

 mesial nematophore varies greatly in length ; considerable differences may be seen even 

 in two succeeding hydrothecse. Sometimes shorter than in the examples figured by 

 Nutting, it may, on the other hand, extend far beyond the margin of the hydrotheca, 

 and, curving gracefully upwards, its tip may reach the level of the upper portion of the 

 rim. There are three cauline nematophores (not two, as Nutting implies) clustered 

 about the stem process on which the hydrotheca rests. Two lie on the anterior surface, 

 one at the distal, the other at the proximal side of the stem process, while one lies on 

 the posterior aspect of the process itself. They are triangular in shape and large, 

 normally with two apertures, one at each of the free angles of the triangle, but 

 occasionally showing, as a variation, a third aperture, situated medianly between the 

 normal two. 



The gonosome is unknown. 



