ON THE HYDROIDS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 533 



in Sertularella gayi as described by Nutting, 1904, p. 6, although I found difficulty in 

 tracing the peripheral tubes to their origin. The peripheral tubes certainly never 

 become hydrotheca-bearing to the same extent as in Sertularella gayi. 



The characters of the trophosome, and especially of the gonosome, appear to indicate 

 close relationship with the Lafoeidae, in which family the genus has accordingly been 

 placed. 



Brucella armata, n. sp. (PI. II. figs. 2a, 2b, 2c.) 



Several specimens have been obtained of a colony for which the above new genus 

 has been formed. The colonies, which are erect and much branched, with both stem 

 and branches thickly fascicled, reach in some cases a height of 6 cm. by a 

 similar breadth. Owing to this great breadth, as compared with height, and to the 

 fact that the many branches lie in one plane, the colony assumes a somewhat flabellate 

 appearance. It is of a pale brown colour, becoming lighter towards the tips of the 

 branches. Except distally, where for a short distance they become monosiphonic, the 

 stem and branches are fascicled, consisting of an axial tube, predominantly hydrotheca- 

 bearing, surrounded by peripheral tubes which may bear occasional hydrothecse and 

 scattered nematophores. The main branches, which may reach a length of 5 cm., leave 

 the stem at irregular intervals, although frequently there is an approximation to 

 alternate arrangement, while those borne by the main branches are regularly pinnate 

 and alternate and are rarely branched. All the branches lie in one plane, and arise 

 from below a hydrotheca, which then lies in the axil of the branch. The cavity of the 

 axial tube is continuous ; the tube is not divided into internodes, but bears 

 alternately at regular intervals small processes to which the hydrothecse are attached. 

 The hydrothecce are biserial, alternate, tubular, with an entire margin which is not 

 parallel to the axis of the hydrocaulus. Their upper side is curved, while the lower is 

 almost straight, and their cavity is cut off from that of the rest of the colony by a 

 strong septal ridge at their junction with the hydrocaulus process. Above this occur 

 one or two delicate, membranaceous intrathecal septa apparently stretching across the 

 cavity of the hydrotheca, while near the edge there are usually two or three lines 

 indicating the presence of marginal reduplications. The length of the hydrothecse from 

 basal septum to margin is between 0*3 and 0*35 mm., while the greatest diameter is 

 from 0*13 to 0'15 mm. Towards the base they become constricted and rest upon a 

 short process of the hydrocaulus, from each side of which springs a nematophore. 

 The nematophores are small, only O'l mm. long by 0'04 mm. in diameter, and 

 resemble those found in some of the Bleutheroplean Plumularians, consisting of two 

 joints, the proximal, a narrow tube, the distal, a wider tube opening out slightly 

 towards the margin, round which there is frequently a reduplication line. This whole 

 two-jointed structure is sometimes loosely incased in an unjointed tube. Scattered 

 nematophores of similar structure occur frequently but irregularly on the peripheral 

 tubes. The form of the hydranth could not be distinguished. 



