REPORT ON THE SIPHONOPHORiE. 253 



(fig. 8, cp), serving for the attachment to the trunk. The two lateral faces of the 

 umbrella, right and left, are strongly convex (figs. 6, 7). 



Nectosac (w). — The subumbrella occupies about two-thirds of the nectophore, and is 

 also strongly compressed in the sagittal direction. Its upper or dorsal face is concave, 

 the lower or ventral convex. Its axial or proximal half is dilated, twice as broad as the 

 abaxial or distal half. The latter opens by a narrow triangular mouth (no), which is 

 surrounded by a small velum (v). The nectocalycine duct (fig. 8, cp), which enters 

 through the pedicle of the nectophore, divides on the top of the nectosac into four radial 

 canals of very different length and form. The shorter concave dorsal canal and the 

 longer convex ventral canal run straight in the sagittal plane ; whilst the two lateral 

 canals (right ex, and left cl) are about three times as long, and form not less than four 

 curved loops, the complicated course of which may best be seen by comparison of figs. 

 6-8. The small ring-canal, which connects the four radial canals at the mouth of the 

 nectosac, makes a simple bend in the dorsal half, a pair of loops in the ventral half 

 (fig. 7, cc). 



Siphosome (fig. 1 drawn from the living specimen ; fig. 2 from the same dead, in 

 contracted state, after detachment of the bracts and nectophores). — The inferior half of 

 the corm, below the nectosome, has the aspect of a flower, which is compressed from two 

 sides, in the same direction as the bilateral nectosome. The trunk of the siphosome 

 (fig. 3, as) is an ovate vesicle, which bears a series of buds (is) in the median line of its 

 ventral side, as an inferior continuation of the superior series of buds of nectophores (in). 

 The polymorphous appendages, which arise from the bud series, are so disposed that 

 immediately beyond the nectosome a corona of bracts is expanded. Below this 

 follows a corona of cystous or mouth-bearing palpons, and inside of these a group of 

 siphons (s) with the tentacles (t) ; finally, at the distal base the bunches of gonophores. 

 When we compare the composition of the siphosome with that of a dichlamydeous flower, 

 then the bracts correspond to the calyx, the cystons to the petals, the siphons to the 

 stamens, and the gonophores to the pistils. If the animal floats quietly at the surface of 

 the sea, then the calyx is opened and the petals and stamens expanded (fig. 1); but 

 when it swims quickly by the action of the nectophores, then the calyx is closed and 

 the appendages included in it form a dense, bilaterally compressed bunch. 



Bracts (figs. 1, 9-12). — The corona of large and firm cartilaginous bracts or covering 

 scales, which expands beyond the nectosome and covers the other parts of the siphosome, 

 exhibits a very remarkable composition, not observed hitherto in any other Siphonophorae. 

 The corona has an amphithect fundamental form, compressed from the two lateral sides 

 of the corm, and is composed of eight foliaceous, symmetrically arranged bracts (fig. 1). 

 A pair of larger and slender lateral bracts (figs. 11, 12) is placed on the two poles of the 

 frontal axis of the trunk (right and left) ; they are 25 mm. long, 5 to 6 mm. broad. 

 A second pair of bracts, which have the same breadth, but only one-third of the length 



