HYDROIDA. BALE. 299 



arranged in regular whorls of three or four, those in each 

 whorl alternating in position with those above and below ; 

 divided into hydrothecate long internodes and intermediate 

 short ones bearing sarcothecse only. 



Hydrothecse very small, cup-shaped, shallow, adnate up 

 to the margin, which is smooth. 



Sarcotheca? large, wineglass-shaped, bithalamic, canalicu- 

 late, moveable ; one in front of each hydrotheca, two laterals 

 above it, one on each intermediate internode, and two in the 

 axil of each hydrocladium, usually one on the proximal inter- 

 node of each branch and one or two on the apophysis. A 

 conical open prominence on the apophysis of each hydro- 

 cladium. 



Gonothecae borne at the bases of the hydrocladia, cam- 

 panulate, very thin and delicate. 



Colour Light brown. 



The above description amends and supplements that in 

 Part II in some minor points. 



From such forms as N. ramosa the species is strongly 

 differentiated by its habit, the pinnate arrangement of the 

 branchlets being very characteristic. A main trunk with 

 all its ramifications occupies a single plane, but where the 

 stem divides into two or three such trunks near the base 

 these may be each in a separate plane. The ultimate 

 branchlets, which fringe each side of the larger branches at 

 very short intervals, may reach an inch or more in length 

 without further subdividing ; when small they are monosi- 

 phonic, and most of them remain so, others become enveloped 

 in the proximal portions by supplementary tubes derived 

 from the parent branch, and so develop into polysiphonic 

 branches giving origin to fresh branchlets. 



A new branchlet commences with a stout apophysis given 

 off by one of the supplementary tubes, then follows a short 

 internode, or occasionally two, without hydrocladia. The 

 first few hydrocladia are generally more or less irregular, 

 those which represent the first whorl, or even the first four 

 or five whorls, being placed unevenly instead of at a uniform 

 height, and only gradually is the normal arrangement 

 attained. The most usual condition is for all the whorls of 

 a single branch to consist of either three or four hydrocladia, 

 but while, as already mentioned, they may be in fours up to 

 a certain point of a branch and in threes beyond it, I have 

 seen no instance of whorls of three being succeeded distally 

 by whorls of four. 



