ON THE HYDROIDS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 81 



sometimes by one or two lines of growth. They are 0'5 mm. in height, and for 0'4 mm. 

 of this distance they are adnate, the free portion curving outwards from the stem. 



Gonosome. The gonangia are ovoid, 0'7 to 0'8 mm. long, and 0'45 mm. in diameter 

 nt the widest part, narrowing proximally and terminated distally by a circular orifice 

 at the end of a short bulging prominence. They lie closely apposed to the stem for 

 the greater part of their length, but can easily be detached, and arise on each side of, 

 and just below, a hydrotheca. Thus although one or two gonangia most commonly 

 occur at one level, the full complement at a plane containing a pair of hydrothecee is 

 four, two to each hydrothecas. 



The colony is of a horn brown colour. 



Locality, etc. Obtained from a gripper on a sounding wire from Scotia Bay, South 

 Orkneys. Depth, 65 fathoms. Date, 25th March 1903. 



Family PLTJMULARIID/E. 

 Aglaophenia dichotoma (Johns.), Kirchenpauer, 1872. (PI. III. figs. 2, 2A, 2B, 2c.) 



A large number of branched, fan-shaped colonies, 10 cm. high by about 7 cm. 

 broad, with monosiphonic stems. The following details supplement KIRCHENPATJER'S 

 rather meagre description : The branching, which is characteristic, is strictly dich- 

 otomous. The stem and branches are divided into short regular internodes 0'3 mm. 

 long, and from a nematophore -bearing process on each of these a hydroclade arises. 

 The hydrodades, which are alternate and closely approximated, are borne on the front of 

 the stem and leave it at an angle of about 45. They also are divided into short regular 

 internodes 0'3 mm. in length, each with two strong septal ridges extending almost around 

 their walls, one opposite and in line with the intrathecal septum, the other at the 

 level of the bases of the supracalycine nematophores. The hydrotheca, which are closely 

 approximated and obconical, are tilted forward from the stem, the distal portion appar- 

 ently being free. Their margin, which is not expanded or flaring, is divided into 

 nine teeth, the anterior three being slightly larger and sharper, the middle one bent a 

 little backwards. The intrathecal ridge is strong and oblique, in the same line as the 

 corresponding internodal ridge, and reaching to the opposite wall of the hydrotheca. 

 The supracalycine nematophores are not quite tubular. They are large and bulging, but 

 do not reach to the margin of the hydrotheca, while the mesial nematophore, which is 

 extremely narrow near the base but becomes wider distally, just reaches the level of the 

 margin, the distal third of its length being free. The process arising from the stem 

 and branch internodes, upon which the hydroclades are borne, bears about five 

 nematophores similar in structure to those on the hydrotheca. The arrangement also 

 is similar, one being median and proximal, while two are lateral and near the distal 

 end of the process, but there are in addition a lateral and a basal pair. 



Gonosome. The corbula is oval, flattened laterally, 2 mm. long by 1 mm. in 



(ROY. soc. EDIN. TRANS., VOL. XLV., 539.) 



