" KNHKAVOUK " SCIKNTII-'K' KKSI'LTS 186 



Colour. Very light brownish, the polypidom very thin and 

 flaccid. 



A little uncertainty exists as to the identity of this Hydroid 

 vvitli Jjiderholm's species, which seems to be of more robust 

 habit, with the branches characteristically recurved. The 

 difference however is not greater than may possibly be accounted 

 for by the ages of the respective forms, and in view of the very 

 close similarity of their minute structure I have not felt iu stifled 



/ d 



in separating them. Jaderholm's specimens were from Japanese 

 waters. 



In most of its characteristics the species differs widely from 

 the previously known Australian species, the ramification 

 especially being quite distinct (though similar to that of 

 H. tubulifera, also described in the present Report). There is in 

 reality no true stem, as distinguished from the branches, but 

 instead we find a succession of branches, each springing from 

 the proximal parr, of the preceding one alternately on opposite 

 sides, and the series of the proximal segments of these branches 

 forms practically a stem, which rnorever becomes fascicled in the 

 manner to be described. If we take any given segment of the 

 upper part of the axial tube we find that at a certain point 

 (a geniculation) it gives origin to a lateral branch. This branch 

 immediately divides, one division continuing upward and out- 

 ward, the other curving round the nxial tube (to which it remains 

 adherent) to the opposite side, where it again subdivides, one 

 division forming another lateral branch, while the other is con- 

 tinued in the form of a supplementary tube, which grows 

 downward in contact with the axial one, thus contributing to the 

 formation of the fascicled stem. From every geniculation, 

 therefore, ascend three free tubes, which in relation to each 

 other, may be described as primary, secondary, and tertiary. 

 They are all alike, having a considerable proximal portion pro- 

 vided with sarcotheca? only, but one of them (the secondary one) 

 soon branches, repeating the scheme of ramification above des- 

 cribed, so that the secondary tube of one axial segment becomes 

 the primary one of the next above. This occurring on alternate 

 sides causes the stem to have a somewhat zig-zag course, the 

 geniculations being about a quarter to a half inch apart, and the 

 branches are free from hydrocladia for a greater distance than 

 this from their origin. The nodes are faint or quite indis- 

 tingiiishable on these portions, but more pronounced on the 

 hydrocladiate parts. 



The branches are all originally monosiphonic, and continue so 

 with the exception of those portions which become part of the 

 stem. The supplementary tubes which, as described above, 

 originate at each geniculation, grow downward towards the base 



