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



huxleiji confer upon this beautiful species an aspect wliicli in gracefulness is pei'haps 

 not surpassed hy any other Plumularian. 



The liydrothecEe are. remarkable from the way in which the orifice lies in a plane 

 parallel to the axis of the supporting internode, instead of being, as in most cases, nearly 

 at right angles to it. The internodes are very short, and the hydrothecjB are consequently 

 brought unusually near to one another. The deep serration of the hydrotheca margin 

 usual in the Statoplean section, here gives place to a shallow crenation, and the very long 

 curved continuation of the mesial nematophore beyond the orifice contributes still fur- 

 ther to the singular aspect of the hydrotheca. In the front of the hydrotheca is a 

 strong parietal fold, having some resemblance to an anterior intrathecal ridge, while the 

 true intrathecal ridge is nearly obsolete. 



The stem and branches, notwithstanding their slenderness, arc polj'siphonic, the 

 accessory tubes ceasing a little before the distal termination of the branches, which then 

 become monosiphonic for the remainder of their course. 



The gonophore can be seen through the walls of the gonangium to be encircled just 

 below its summit by a WTcath of refringent spherules, sunilar to those to which Kirchen- 

 pauer first drew attention in the gonophore of his macrorhynchial section of Aglaophenia. 

 He believed them to be confined to this group, and incorrectly regarded them as ova.^ 



The phylactocarps are for the most part longer than the hydrocladia, and with the 

 symmetrical arrangement of their parts are objects of great beauty, while they are full of 

 interest in the evidence they afi'ord of the extent to which various parts of an organism 

 may become modified in order to fit them for a change of function." 



]\Ir. Busk has identified the present species with the Phnnularia liuxleijl of the 

 voyage of the "Rattlesnake," ''and a comparison of the Challenger Hydroid with authentic 

 specimens from the collection made during that voyage, has enabled me to confirm this 

 determination. 



Dredged at Station 188, September 10, 1874, lat. 9° 59' S., long. 139° 42' E.; depth, 

 28 fathoms; bottom, mud. Also at Station 190, September 12, 1874, lat. 8° 56' S., 

 long. 136° 5' E.; depth, 49 fathoms ; bottom temperature 23°"9 C ; bottom, mud. 



Aglaophenia, Lamouroux {in part). 



Plumularia, Lamarck, Hist. Nat. des An. sans Vert., 1815. 

 Aglaophenia, Lamouroux, Hist, des Pol. Coral, ilex., 1816. 



Aijlaophenia macgillivrayi, Busk, sp. (Pis. X. and XX. figs. 4-6). 



Plumularia macgilliDrayi, Busk, Voyage of the " Eattlesnake," vol. i. p. 100, 1852. 

 Tropliosome. — Colony attaining a height of upwards of fifteen inches ; stem fascicled, 



' Kirchenpauer, he. cit., Band v., Ueljer die Hydroidenfaniilie Plumularidce, p. IC. 

 - See general remarks on the morpliolog)' of the Phylactooarp, p. 10. 

 3 Busk, Voj-age of the "Rattlesnake," vol, i. p. 395. 



I 



