274 EENEST WAEEEN. 



branches, and also at intermediate places. The diameter of 

 the hydrocaulus is about 0*10 mm., and the thickness of the 

 perisarc 4*4 ju. 



Hydranth. — The polyp has the typical eudendrium-shape, 

 and there are 15-18 tentacles in a single verticil. 



In preserved specimens the trumpet-shaped hypostome 

 measures about 0'09 mm. in height and 0"25 mm. in diameter. 

 The body of the hydranth, measured from the verticil of 

 tentacles to the base, has a height of about 0'39 mm., and its 

 greatest breadth is about 0"32 mm. 



GrONOSOME. — The male only has been found. The gono- 

 phores are carried in dense clusters on very short annulated 

 stems, which spring direct from the hydrorhiza (text-fig. 1, B). 

 Each cluster may be regarded as arising from an abortive polyp. 



The gonophores are three-chambered (PI. XLV, fig. 4) ; the 

 proximal chamber is generally very small. There is some- 

 times a tendency for the development of a slight terminal 

 tubercle, but no nematocysts have been seen in such. 



The length of a gonophore is about 0'57 mm., and the 

 diameter of the distal chamber 049 mm. 



General histology. — There is a shallow groove running 

 round the hydranth at about one third of the height of the 

 polyp above the base (PI. XLA-^, fig. 1, t.pr.). A thin continua- 

 tion of the perisarc of the hydrocaulus is present over the 

 base of the hydranth, and it terminates in this shallow groove 

 (figs. 2 and 3, t.pr.). The ectoderm below the groove diifers 

 somewhat in character from the ectoderm above, and it ends 

 in a line of especially large cells (cc), which have large 

 nuclei and stain deeply. The perisarc of the hydrocaulus 

 consists of an inner and outer layer (fig. 2, ^^2 and pi), and it 

 is the latter (pj which is continued upwards over the base of 

 the hydranth. Allman states that in Eudendrium vagi- 

 natum Allman "the body as far as the origin of the 

 tentacles " is " enveloped in a loose corrugated membranous 

 sheath, which loses itself below on the hydrocaulus." ^ The 



' AHman, G. J., 'A Monograpli of the Gymnoblastic or Tulnilarian 

 Hydroids,' Part II, p. 339. 



