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



corruidia, and branching irregularly, giving off a special canal to each branch of the 

 gonodendron and to each gonophore budding from it. (11) The palpon canal (PI. IV. fig. 

 18, q), the simple blind cylindrical cavity of the gonopalpon, which arises from the distal 

 end of each gonodendron. (12) The gonophore canal, running through the pedicle of each 

 gonophore to the centre of its subumbrella, and dividing there into four radial canals which 

 are united at the margin by a ring-canal. (13) The spermarial canal (PI. VII. fig. 46), 

 or the simple central cavity in the axis of each androphore (spadix), arising from the 

 centre of its subumbrella and being the direct prolongation of the gonophore-canal. (14) 

 The ovarial canal, arising from the centre of the subumbrella of each gynophore (as the 

 prolongation of its pedicular canal), and running either in the axis of the ovarium as a simple 

 spadix (PI. II. figs. 9, 10, c), or forming an irregular network of spadicine canals around 

 the egg. 



Gonodendra. — The corms of the Auronectae are monoecious, the cormidia monoclinic, 

 and the gonodendra monostylic. Each cormidium bears in the small Stephalidae a simple 

 gonostyle with a single gonopalpon (g), a single androphore (h), and several gynophores 

 (/), usually between ten and twenty (PI. VI. figs. 32-38 ; PI. VII. figs. 48, 49). The 

 large Rhodalidae, however, bear on each cormidium one or two clustered gonodendra, 

 each branch of which corresponds to the small monostylic gonodendra of the Stephalidae, 

 and is composed of a few androphores and a greater number of gynophores ; usually a 

 single large gonopalpon is attached to each gonodendron (PI. I. figs. 2, 3 ; PI. II. figs. 

 6-12; PI. IV. figs. 15, 18). 



Gonostyles (PI. I. figs. 2-5 ; PI. II. figs. 7, 8 ; PL VII. fig. 49, ab).— The stems of 

 the gonodendra, or the branched gonostyles, are in the Auronectae very thick-walled 

 cylindrical tubes, which arise from each cormidium near to the base of the siphon, on its 

 axial side (fig. 48). The wide axial canal of the gonostyle (figs. 2-4, c) is convoluted 

 spirally in the highly contracted spirit specimens examined, and surrounded by a strong 

 muscular wall of remarkable thickness. The transverse section of this wall (PI. I. figs. 

 4, 5) exhibits the same structure as the pedicle of the siphons. An inner thin layer of 

 ring-muscles (mc) and an outer thick layer of longitudinal muscles (ml) are separated by 

 a thick elastic fulcrum (z). This fulcral plate arises outside in the form of numerous 

 branched radial lamellae. The stem must be very expansible and contractile in the 

 living animal. The branching of the gonostyles is unilateral in the small Stephalidae 

 (fig. 49), dichotomous or irregular in the large Rhodalidae (figs. 3, 7, 8, 15). 



Gonopalpons (PI. I. fig. 2, r ; PI. IV. figs. 15, r, 18, q ; PI. VI. figs. 37, 38, q).— The 

 single form of palpons or tasters, which occur in the Auronectae, are the sexual palpons 

 or " gonopalpons." Usually (or always V) a single tubular gonopalpon is attached to 

 each cormidium, as a distal branch of its gonostyle ; it is a simple cylindrical tube closed 

 at the pointed distal end (fig. 18, q). The gonopalpons seem to be very contractile, but 

 were for the most part detached and lost in the specimens examined. 



