HTDEOID ZOOPHYTES. 19 



Hydrosome. — A solitary zooid. The hydrocaulus is about 8 mm. in height and 

 about 2 mm. in diameter for the greater part of its length. At the base it is much 

 thinner and gives off numerous hydrorhizal filaments (fig. 18, hrh. f.) for attachment 

 to the sponge spicule debris. It is covered throughout its length by a thin chitinous 

 perisarc with transverse striations. 



The hydranth is naked, about 6 mm. in length, and spindle-shaped, thickening 

 gradually from the hydrocaulus, and then gradually tapering to form the conical 

 hypostome. The distal half of the hydranth bears numerous short, thick, scattered 

 conical or hemispherical tentacles (fig. 18, t.) the largest of which are situated just 

 above the thickest part of the hydranth. 



Gonosome. — No gonophores are present. 



Although we are unable to give a generic or specific name to this specimen, we 

 are anxious to record the existence of a member of this family in the Antarctic Sea. 

 Hartlaub, in his summary of the Southern Hydroids, does not mention the family at 

 all, but Jaderholm (13 : p. 2.) records the occurrence of M. austro-geurgiae from 

 South GeQrgia. 



FAMILY SERTULAEIIDAE. 



Sertularella spiralis. 

 (Plate III., figs. 19, 20.) 



Locality.— W.Q., No. 10 hole, July 3rd, 1903 ; 130 fms. 



Several fine colonies of this species were obtained from this hole at the date 

 given above. It is perhaps noteworthy that no other specimens were obtained from 

 any other localities, although at this particular spot the species seems to have 

 been so abundant. Unfortunately, all the colonies were torn away from their 

 attachments, so that in some particulars our description must be imperfect. 



Hydrosome. — The slender monosiphbnic hydrocaulus is 250 mm. or more in 

 height. It is bent alternately right and left at intervals of 5 mm., and at each 

 geniculation two branches are given off from the major angle. Each of these 

 branches is about 40 mm. in length, slightly geniculated and pinnately branched, 

 the pinnules arising as before from the neighbourhood of the angles. Their internodes 

 are about 2 • 5 mm. in length. In some cases one or both of the branches themselves 

 are elongated to form an axis similar to the main axis and give rise to secondary 

 branches similar to the primary branches. 



The general effect of this method of ramification is to give the appearance of 

 a spiral form similar to that so characteristic of the genus Hydrallmania. 



The pinnules vary in length up to 30 mm. and are divided into a series of 



internodes by geniculations, but these internodes are not all of the same length 



(0- 6-1-0 mm.), increasing somewhat in length in the distal parts. Proximally the 



nodes are not very clearly marked. 



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