308 ERNEST WARREN^ 



in the middle of the outer surface. Aperture somewhat con- 

 tracted, directed outwards ; two rounded abcauline teeth. 



Length, measured along abcauline edge, 0*293 mm., greatest 

 breadth 0*172 mm. Distance from mouth to mouth of a pair 

 of hydrothecse 0'570 mm, 



Hydranth. — About 12-15 tentacles. Nematocysts, few, 

 small, and inconspicuous, about 4"l/i in length, and 1'2 /i in 

 breadth. 



Gonosome. — Gonangia ovate, upper surface flat or slightly 

 convex ; 7-9 prominent transverse annulations, aperture wide, 

 operculate. 



Length about 1*62 mm., breadth 0"8-47 mm. The enclosed 

 blastostyle is branched. 



The above description agrees with that given by Bale, 

 except that the gonangium in the Australian hydroid appears 

 to have 4-5 ridges in place of 7-9, 



Histology, — In the black variety the eudoderm is pro- 

 vided with dark l)rown, opaque, pear-shaped masses (PI. 

 XLA^III, fig, 37, c.p.). These are, doubtless, cells, but I have 

 not with certainty detected the nucleus. The colouring 

 matter may be very opaque and compact, but sometimes it is 

 seen in the form of granules, 



(18) Sertularia linealis ,s-p,j/. 



The hydroid is characterised by running in longitudinal 

 lines over the surface of ribbon-like sea-weeds. It is of a 

 dark brown or black colour, and it does not appear to attain 

 to a height of more than about one fifth of an inch. It was 

 collected in the rock pools at Kosi Bay, Zululand, 



Tkophosome, — Hydrorhiza runs in longitudinal lines con- 

 nected together by occasional cross-branches (text-fig, 9,^4), 



Diameter about 0"23 mm. The outer layers of the perisarc 

 may become remarkably diffuse and swollen. The inner 

 compact portion has a thickness of about 18 //, and the diffuse 

 outer portion 47 ^, 



Hydrocaulus. — It consists of short upright stems divided 



