42 THE VOYAGE OF H.M.S. CHALLENGED. 



Lytocarpus seciuidus, Kirchen. (PL XIV.). 



Aglaajthenia (section Lijtucarpiu) sccunda, KirclieBpaue», Abliandl. ;xus duiii (.'icbicte dur Natur- 

 wiss. voii dein natur\viss. Verein in Hamburg, Band v. 1872. 



Tivjjhosome. — Colony attaining a. height of more than two and a half feet ; main .stem 

 ftiscicled, rooted by an taitangled mass of fibres, and emitting, along nearh' its entire length, 

 short Ijranches which carry the hydrocladia, and which, though regularly disposed in alter- 

 nate pinnsp, are all directed towards the same side of the stem ; hydrocladia about two- 

 tenths of an inch in length. Hydrotheca3 rather deep, with crenate margin ; hydrothecal 

 ridge short and broad, situated near the base of the hydrotheea; mesial nematophorc adnate 

 to the hydi'otheca walls for al)Out two-thirds of the height of the walls, and terminating 

 as a short, free, blunt spine, which does not reach the level of the hydrotheea margin ; 

 lateral nematophores thick, s}iout-shaped processes not overtopping the hydrotheea. 



Gonosome. — Phylactocarps replacing the hydrocladia at sliort intervals along the 

 hydrocladia-bearing Ijranches, each consisting of a jointed rachis, supporting on every 

 alternate internode a long curved spine, which carries from its base to its apex a double 

 series of wide cup-shaped nematophores, similar nematophores being also borne by the 

 rachis. 



No gouangia were present in the specimens. 



Lytocarpus secundus is a remarkable and l)eautiful Hydi-oid, rendenal very striking by 

 its large size, and by its regularly disposed primary branches. These are each about 

 two inches in length, and though at their origin given ofl" as pinna) from opposite sides of 

 the stem, become all directed towards one side, thus giving a secund character to the 

 ramification. In some of the larger .specimens a few branches arc given off irregularly 

 towards tlie base of the stem. 



Another very striking feature is found in the curious comb-like phyhictocarps. These 

 are shorter than the hydrocladia, generally about half their length, and their rachis, like 

 that of the hydrocladia, consists of a consecutive series of nearly ecj^ual iuternodes, which 

 in the phylactocarp are about eighteen or twenty in number. From the same side of 

 every alternate internode there is sent off a short thick process which supports the long 

 slightly curved spine, the spines thus carried in a single series along the rachis giving to 

 the phylactocarp its resemblance to a comb. Large regularly disposed cup-shaped 

 nematophores are arranged from the base to the apex of the spine in two alternate or 

 sub-opposite series. The spine is itself hollow, with a terminal orifice. Nematophores 

 entirely similar to those of the spine are scattered over the rachis. 



Though no gonangia were developed in the specimens, I take it for granted that the 

 comb-like organs are true phylactocarps. The sinne-like appendages (the teeth of the 

 comb) arc probably the representatives of the mesial nematophores of suppressed 

 hydrotheea;. 



