ON THE HYDROIDS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 83 



marked angle at which each thecate internode lies with regard to the one preceding it, 

 gives these simple distal hydroclades a helicoid-cyme-like appearance. In the proximal 

 hydroclades and here our specimens differ from HARTLAUB'S two processes arise below 

 and at the opposite sides of the first hydrotheca, each of which bears a thecate internode, 

 so that after the first hydrotheca the hydroclade possesses two diverging branches each 

 similar to the simple distal hydroclades. Since the double hydroclades arise laterally 

 and not dorsally. as HARTLATJB describes, from their internode, it follows that their 

 origins lie in a plane at right angles to the plane of the primary stem processes. The 

 hydrothecse are shallow, with delicate, slightly expanded walls, and smooth margins. They 

 appear to terminate the internode which bears them, are fixed only by their bases to 

 their internode, and their walls are free. A single delicate, shovel-like nematophore lies 

 in the centre of the internode beneath each hydroclade. 



Gonosome. Not observed. 



The structure of the whole colony is extremely delicate. In some cases the 

 hydrothecal and internodal walls collapsed in process of mounting for microscopic 

 examination. 



Locality, etc. Growing on a sponge, Port Stanley, Falkland Islands. 3rd February 

 1904. 



Previous Localities. South of Tierro del Fuego and Island Pictou, Tierro del 

 Fuego Archipelago. 



Plumularia pinnata, Linnseus, 1758. 



A number of colonies, the largest only about 4 cm. high, occur on sponges and on 

 lamellibranch shells. The colonies agree with HINKS'S description. The following 

 variations were noted in the specimens : Generally the number of hydroclades per 

 internode is two, but on a number of the distal intern odes only one hydroclade occurs. 

 The presence of a basal athecate internode at the origin of each hydroclade, as described 

 by BILLARD (1904, p. 204), was noted, but between the thecate internodes no inter- 

 mediate athecate internodes were observed. 



Gonosome. While the proximal, and therefore the older, gonangia assumed the 

 spinous form figured by HINKS (1868, PL 65), the distal, younger gonangia were some- 

 what cup-like, with a truncated appearance, due to the inversion of the topmost portion 

 of the gonangium, which, at first inverted, apparently becomes everted in the later 

 stages of growth. 



Locality, etc. Growing on sponges and on lamellibranch shells, coaling jetty, 

 Cape Town Docks. May 1904. 



Plumularia unilateralis, n. sp. (PL II. figs. 1, IA, IB, Ic.) 



The specimens for which this species has been formed are small, averaging only 

 2 cm. in height, with simple recurved stems divided by slanting nodes into regular 

 internodes, in general 0'4 mm. in length, but rather longer towards the base. From the 



(ROY. soc. BDIN. TRANS., VOL. XLV., 541.) 



