REPORT ON THE SIPHONOPHOR-ffi. 265 



The two former run simply curved in the median plane of the nectosac ; the ventral is 

 shorter than the dorsal. The two symmetrical lateral canals are much longer, each 

 about three or four times as long as each of the sagittal canals ; they pass into the two 

 large lateral lobes of the nectophores, where they form half a dozen loops ; their compli- 

 cated course will be intelligible by comparison of figs. 2, 3, and 4. The small ring- 

 canal which unites the equidistant distal ends of the four radial canals is elliptical and 

 lies above the insertion of the velum (fig. 4, cc). 



Siphosome (PI. XX. fig. 9, apical view, from above ; fig. 12, basal view, from below ; 

 figs. 10, 11, 13, ventral and half-lateral view, in different states; all the figures twice 

 natural size. In PI. XIX. fig. 1, the trunk of the siphosome is completely covered and 

 hidden by the cormidia). — The trunk of the siphosome is a large reniform bladder, or an 

 inflated disc of rose colour, subhorizontally expanded and depressed in a vertical direction ; 

 its breadth (30 mm.) is about twice as great as its height (15 mm.). The wide cavity of 

 the thin-walled bladder is closed, filled with chyle, or the fluid of the gastrocanal-system, 

 and communicates only at its apex with the base of the trunk of the nectosome, and by a 

 peripheral corona of numerous small pores with the cavities of the cormidia. A com- 

 parison of figs. 9-13 in PI. XX. demonstrates that the kidney-shaped and spirally 

 twisted disc, from which the name Discolabe is derived, is nothing other than the inflated 

 trunk of the siphosome twisted up in a low and broad spiral ; the turning of the spiral 

 is dexiotropic (delta-spiral), opposite to that of the trunk of the nectosome, the necto- 

 phores of which are arranged laeotropically (lambda-spiral). The trunk of the siphosome 

 in Physophora is described erroneously as a lambda-spiral by Claus (74, p. 13, Taf. iii. 

 figs. 1-4). The spiral of the latter is also dexiotropic, but flatter and less developed than 

 in Discolabe; in the largest specimens of the latter two complete turns may be dis- 

 tinguished (fig. 12). The superior or proximal face of the discoidal bladder is covered 

 in the living animal by the base of the nectosome, the inferior or distal face by the axial 

 parts of the cormidia, whilst the abaxial parts of the latter form a splendid corona around 

 its peripheral margin. 



Cormidia. — The number of ordinate cormidia covering the trunk of the siphosome 

 is in the smaller specimens of Discolabe ten to twenty, in the larger thirty to fifty or more, 

 besides the numerous small buds of undeveloped cormidia which arise from the blastocrene 

 or the point of vegetation situated at the top of the siphosome. Beginning from this point, 

 the age of the succeeding cormidia increases gradually, so that the lowermost (at the 

 distal end of the trunk) are the oldest. These, however, are not the largest ; the size of the 

 cormidia is the greatest in the middle of the spiral series, and decreases towards the two 

 ends of it. The peripheral margin of the spiral bladder, to which the articulated series 

 of the ordinate cormidia is attached, is the ventral median line of the trunk of the siphosome. 

 It appears elegantly facetted and regularly segmented after the detachment of the covering- 

 corona of palpons ; the size of these polygonal articular facettes, the largest of which are 



(ZOOL. CHALL. EXP. PART LXXVII. — 1888.) Hhhh 34 



