20 THE VOYAGE OF H.M.S. CHALLENGER. 



branches fascicled, liydrocladia springiDg from the brauclies at distant and iiTegiilar inter- 

 vals, and being themselves set with rather distant, pinnately-disposed alternate hydrocladia. 

 Hydrothecae campanulate, every internode of the hydrocladia carrying a hydrotheca, which 

 is adnate to the supporting internode for about two-thirds of its height ; lateral nemato- 

 phores very short, cup-shaped, not reaching the margin of the hydrotheca ; mesial 

 nematophores like the lateral in form, one borne by every internode at the proximal, and 

 one at the distal side of the hydrotheca. 



Gonosome not known. 



Plumulana laxa is a very remarkable form, rendered striking by its somewhat diffuse 

 habit, and by the doubly pinnate arrangement of its hydrotheca-bearing ramuli. 



In this doubly pinnate condition of the hydrocladia we have a very exceptional 

 character, for though it is not unusual among the Plumularidse for the ultimate hydro- 

 thecal pinnae to be borne by ramuli also pinnatcly disposed on the main stem or primary 

 branches, such ramuli rarely carry hydrothecse. The primary hydrocladia of the present 

 species vary in length from about three-tenths to six-tenths of an inch ; the secondary 

 hydrocladia attain a nearly constant length of about two-tenths of an inch. 



■ Dredged in Station 163, April 4, 1874, lat. 36° 56' S., long. 150° 30' E. ; 120 

 fathoms. 



Plumularia dolichotheca, n. sp. (PI. I. figs. 7, 8). 



Trophosome. — Colony attaining a height of about three inches, stem irregularly 

 branched, monosiphonic, hydrocladia alternate, about two-tenths of an inch in length, 

 divided into internodes of unequal length, each carrying one, two, or three hydrothecse. 

 Hydrothecae deep, thimble-shaped, adnate to their internodes by their entire height, and 

 with the lateral nematophores springing from a point close to the margin of the hydrotheca ; 

 mesial nematophore sub-calicine only, and found only below the proximal hydrotheca of 

 the internode. 



Gonosome not known. 



Plumularia dolichotheca presents several very unusual characters. It is, with the 

 exception of Pliimtdaria frutescens of the European shores, the only Plumularian with 

 which I am acquainted in which more than one hydrotheca is carried by one and the same 

 internode. While in the present species some of the internodes of a hydrocladium carry 

 as usual only one hydrotheca, others carry two, or even three. When two or more hydro- 

 thecse are carried by a single internode, it is only the proximal hydrotheca which is sub- 

 tended by a nematophore. This nematophore is supjjorted on a small tubercle-like process 

 of the internode, while the corresponding points below the more distal hj'drothecse show no 

 trace of the tubercle, a fact which affords evidence that the absence of the nemato2:)hore 

 is not due to its having been accidentally detached. 



Under the name of Plumularia cylindrica, Kirchenpauer describes a species — also from 



