ON THE HYDROIDS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 11 



broken off not far from their origin, while the greater number of the stems are covered 

 with polyzoon growths. 



Silicularia hemispherica = HyjKinthea hemispherica, AUman, 1888. 



The only representative of this genus in the Scotia collection occurs on the frond of 

 Macrocystis pyrifera, from Gough Island. The specimens bear out Hartlaub's 

 opinion that the length of the peduncle, varying as it does to a considerable extent, is 

 not a safe specific character, for here various peduncles measure 6, 5, 4, 3, 1 mm. 

 In so simple a genus distinctive specific characters are not easily obtained, but the 

 following point to identity with S. hemispherica : — Hydrocaulus, creeping, branched, 

 bearing at varying distances pedunculate hydrothecse and gonangia which usually 

 alternate with one another. The peduncles are exceedingly variable in length, rather 

 less in diameter than the hydrocaulus, with a distal swelling, succeeded by a globular 

 segment, and this in turn by the hydrotheca. The hydrotheca is conical, almost as 

 broad as long, about 07 mm. high by 0'5 mm. in greatest diameter, with a markedly 

 oblique margin. 



The gonangia are 2 mm. long by 0*6 mm. in diameter, narrowing slightly towards 

 the opening, and considerably towards the base, where they are supported by a distinct 

 peduncle. They are never grouped on the hydrocaulus. 



Locality, etc. — Creeping over the fronds of Macrocystis pyrifera, Gough Island. 

 Lat., 40° 20' S. ; long., 9° 56' W. Date, 22nd April 1904. 



Hebella sti'iata, Allman, 1888. (PI. I. fig. 7.) 



Several specimens of the beautiful species described by Allman in the Challenger 

 Reports occur creeping on the stems and branches of various larger Hydroids. The 

 hydrothecae are large, almost 1 mm. in length by from 0"22 to 0'25 mm. in 

 diameter, cylindrical, borne on short, untwisted peduncles varying in length from 0*25 

 to 0"4 mm. In some the characteristic ringing exists only on the lower half of 

 the wall, part towards the margin being smooth. The hydranths are in all cases con- 

 tracted, and in this state occupy only the lower half of the hydrotheca. They are in 

 good condition, and show in their contracted state a bulging body, separated from a 

 fleshy disc at the base of the hydrotheca by a marked constriction, and surmounted by 

 another constriction from above which arises a whorl of tentacles. Within the 

 tentacles there arises a conical hypostome. 



Gonosome. — Not present. 



Locality, etc. — Creeping on the stems and branches of Lafoea gracillima, Grammaria 

 magellanica, Sertularella jiliformis, Burdwood Bank. Lat., 54° 25' S. ; long., 57° 32' 

 W. ; 56 fathoms. 1st December 1903. 



(ROr. SOC. EDIN. TRANS., VOL. SLV., 529.) 



