REPORT ON THE SIPHONOPHOR^E. 217 



in Stephanomia and Crystallodes, where they form a single rectilinear series in the 

 ventral median line of the rigid trunk ; all parts of the cormidia here hang down from 

 its ventral or inferior side, whilst the dorsal or superior side is only covered with bracts 

 (PL XVII. fig. 1). Anthemodes and Cuneolaria differ from the former in the spiral 

 twisting of the prolonged and very movable stem ; the cormidia, therefore, are turned 

 in all directions; but they are also separated by long internodes which are only covered 

 with bracts (PL XIV.). Each cormidium is composed in these four genera of a single 

 siphon with its tentacle ; one or more palpons (or cystous), usually each with a palpacle; 

 a group of bracts, and a monoclinic pair of distylic gonodendra (a male and a female) 

 (PL XV. fig. 5,/, h; PL XVII. fig. A, J] h). 



The Halistemmidse — or the Agalmidae with dissolved cormidia — comprise the 

 majority of this family, viz., all the genera except the four above mentioned. The poly- 

 morphous persons and their organs are here more or less dislocated and scattered ; the 

 palpons and gonostyles arise (singly or united in groups) directly from the trunk of the 

 siphosome, not from the base of the siphons as in the Stephanomidas. Usually also 

 here the internodes between the siphons are of equal length ; they are, however, not 

 free, but covered with palpons, cystons, and gonodendra variously arranged : some- 

 times rather regularly (as in Phyllophysa, Cupidita, &c.) ; at other times very 

 irregularly (as in Halistemma, Agalmopsis, &c). A peculiar structure already described 

 by Eschscholtz (1, p. 150) is developed in Agcdma, where the bracts compose a scale, a 

 carapace with a central cavity, or an axial hydrcecium into which the distal part of the 

 siphosome may be retracted (PL XVIII. fig. 8). 



Bracts. — The hydrophyllia or " covering scales " in all Agalinidse are very 

 numerous, often several hundreds, in the largest forms more than a thousand. They 

 arise usually not only from the nodes of the trunk, where the siphons are attached, but 

 also from the internodes between them. The carapace of scales, which is composed of 

 the jointed bracts apposed one to another, is always complete in the contracted state of 

 the siphosome, and often also in the expanded state. Their special form and arrange- 

 ment are very different in the various Agalmidse. Generally the bracts are thick, 

 prismatic or wedge-shaped in the Crystallodinas, where they cover the rigid trunk 

 so densely that their intervals nearly disappear and the siphosome loses its contrac- 

 tility. In the Anthemodinse, on the other hand, where the stem is very extensUe 

 and contractde, the bracts are usually thin, fofiaceous or squamous, and the intervals 

 between them of very variable size. The general form of the bracts is sometimes 

 ovate, lanceolate, or rhombic, at other times trigonal, tetragonal, or pentagonal, often 

 with three to five (rarely more) prominent teeth at the distal margin. Usually the 

 superior or outer face is more or less convex (often with prominent ribs, armed with 

 cnidocysts), the inferior or inner face concave ; near this runs in the median line of the 

 bract the simple blind bracteal canal. The clear and hyaline jelly-substance of the 



(ZOOL. CHALL. EXP. — PART LXXVII. — 1888.) Hhhh 28 



