306 ERNEST WARREN. 



The internodes, bearing* a pair of hydrotheca?, are distinguish- 

 able by the presence of nodes only on the terminaT branches. 

 In the older branches and main stems they are not present. 



Diameter of main stem at the base 0*24 mm., thickness of 

 perisarc 36^ ; terminal branch, diameter 0*20 mm. 



Hydrotheca. — In pairs, opposite, not in contact, tubular, 

 slightly divergent, adnate nearly up to the margin ; two 

 spine-like abcauline teeth, the back one being the larger 

 and slightly incurved. Operculum two flaps. 



Length of hydrotheca, measured along the outer edge, about 

 0-640 mm., greatest breadth 0*202 mm. 



Hydranth. — About 18 tentacles. 



CtONOSOME. — Gonangia, long, ovate, aperture operculate with 

 a slightly elevated border. 



In the male, length l"414mm., breath O'SOo mm., thickness 

 of perisarc 7 /u. 



The above description only differs from that given by Bale 

 in connection with colour, absence of nodes in the older stems, 

 and the mention of an operculum. 



It may be noticed that in the figure given by Hincks ^ the 

 nodes are not shown. 



(17) Sertularia loculosa Bti.sl-. (PI. XL VIII, fig. 37.) 



Sertularia loculosa Busk, ' Yoy. of Rattlesn.,' 1852 ; Bale, W. M., 



' Cat. of Axistr. Zoopli.," 1884, p. 91. 



This is a common hydroid on the Natal coast; it occurs on 

 coralline and other seaweeds. The colour of the colony is 

 sometimes almost black, and at other times a pale brown. It 

 is not certain whether the difference in colour is due to 

 different physiological and histological conditions which may 

 occur at different times in the same colony, or whether the 

 two forms indicate two distinct varieties. There is no obvious 

 difference in the ordinary specific characters in the two kinds. 

 The height is about half an inch. 



1 Hincks, T., ' British Hydroid Zoophytes,' 1868, PL LIY, h. 



