14 SYDNEY J. HICKSON and F. H. GEAVELY. 



Hydrosome. — The hydrocaulus spriags from a hydrorhiza composed of thin 

 branches ramifying in a sponge. The hydrocaulus is unbranched, and rises to a 

 height of about 40 mm. It is of almost uniform diameter throughout. 



The perisarc is thin, membranous, and ends rather abruptly a little below the 

 hydranth, which is marked off from the hydrocaulus by a slight constriction. The 

 height of the cylindrical hydranth is about 5 mm. There is a dense tuft of about 

 60 tentacles round the mouth. The proximal circlet is composed of about 25 tentacles, 

 7 mm. in length. 



Gonosome. — There are about nine bunches of closely packed spherical gonophores 

 attached in the usual manner to the inner or distal side of the proximal circlet of 

 tentacles. From the position they occupy in the spirit specimen lying close alongside 

 the wall of the hydranth, it seems probable that in life the hydranth was pendulous. 

 The blastostyles are about 5 mm. in length and the gonophores are 0*9 mm. in 

 diameter. The structure of the gonophores is extremely interesting. The umbrella 

 wall consists (fig. 34) of an outer layer of simple ectoderm, a thin layer of mesogloea, 

 and an inner layer of ectoderm cells, which appear to be tri-radiate in section, one of 

 the radii projecting into the mass of sperm cells, and the other two radii forming a 

 continuous thin membrane lining the sub-umbrella cavity. At the distal extremity 

 of the gonophore the inner and outer ectoderm layers are continuous, and between 

 them the umbrella wall is thickened and contains a ring of endoderm cells. In some 

 cases there are four short tentacular thickenings of the ectoderm at the mouth of the 

 gonophore (fig. 34). In the centre of the gonophore there is a well-marked manubrium 

 or spadix, with a lumen and without any clearly-defined ectoderm covering. The 

 sperm cells entirely fill the space between this endodermal spadix and the umbrella 

 wall. The sperm cells lying in contact with the manubrium are evidently in the 

 earlier stages of spermagenesis, those lying at the periphery of the sub-umbrella 

 cavity in the later stages of spermagenesis (fig. 34, sp.), so that it may be said that 

 the sperm cells ripen from within outwards. 



The absence of any well-defined canals in the gonophore, and the presence of 

 four conical rudimentary tentacles, suggests afiinities with Agassiz's sub- genus 

 Thamnocnidia (1 : see 2, pp. 399-400, 406, and 416), but apart from this it is not 

 possible to find any close affinities with other species of the genus. 



TUBULARIA L0N6STAFFI. 



(Plate II., fig. 11.) 



Locality.— ^o. 6 hole, April 8th, 1903; 124 fms. 



Only a single specimen of this magnificent Tubularian zoophyte was found, and 

 it bears unfortunately only a single hydranth. As it appears to be quite distinct 

 from Tuhularia hodgsoni and does not agree with any other species of the genus 

 that has hitherto been described, we propose to call it Tuhularia longstaffi.. 



