REPOKT ON THE SIPHONOPHORJE. 193 



The simple terminal filament is permanent in the majority of the Physonectae (in all 

 Forskalidse, a great part of the Agalmidse, Stephanomia, Anthemodes, PI. XV. fig. 11, 

 Cupulita, &c.), some Anthophysidae, &c. But in another great part of the genera it 

 becomes trifid and developed in the form of three terminal appendages, an odd median 

 vesicle (or terminal ampulla) and two paired lateral filaments or horns (Crystallodes, 

 PI. XVII. figs. 4, 5, Agalma, PI. XVIII. fig. 14, Agalmopsis, &c). To these three 

 appendages is added in Athorybia a peculiar conical solid appendage, a dorsal spur 

 (PI. XII. figs. 12, 13, tf), and in the closely allied Antlwphysa a pair of two lateral 

 palmate appendages on the dorsal side. The remarkable Agalmid Lyclmagalma is 

 distinguished by a large hydrostatic terminal ampulla, and a corona of eight radial 

 filaments surrounding it (PL XVI. figs. 1, 9). 



Palpons. — Hydrocysts or tasters are generally present in all Physonectse, and usually 

 in far greater number than the siphons, so that each cormidium possesses a group of 

 several palpons (PI. XII. figs. 7-9, q ; PI. XVIII. fig. 2, q, &c). The true palpons or 

 tasters are, however, often confounded with other organs, especially with the cystons 

 and even with the tentacles (Glaus, 34, 35, Sec). The true palpons are mouthless, cylin- 

 drical, pyriform or spindle-shaped tubes, which morphologically correspond to the 

 manubrium of a Medusa, but not to the tentacle. They differ from the siphons as well 

 as from the cystons, in the absence of a distal opening ; also from the former in the 

 simpler structure of their thin very contractile wall, and especially in the absence of 

 hepatic glands, and of a basigaster. Sometimes, however, two annular constrictions are 

 more or less distinct, so that a short pedicle, a middle main part and a distal appendage 

 or terminal ampulla may be distinguished. The latter often exhibits various structures, 

 an accumulation of terminal cnidocysts, of pigment, of palpoblasts, &c. The main function 

 of this distal part seems to be sensory, mainly feeling; sometimes an ocellus is developed 

 on its dorsal side, provided in some species with a small lens (PI. XI. fig. 4, qo) ; at 

 other times the spherical distal end is separated by a constriction from the main part 

 and contains a group of crystals or concretions, rotated by vibratile epithelium, thus 

 resembling an otocyst. The largest palpons are developed in the Discolabidaa (PI. XIX. 

 fig. 1), where they replace the missing bracts ; they form at the proximal end of the 

 siphosome a corona of very large and thick- walled protecting tubes, which are at the 

 same time vigorous capturing arms ; each ordinate cormidium possesses either two 

 palpons (Physophora) or a single large one (Discolabe). Another part of the palpons 

 has a direct relation to the gonophores, and the gonostyles may be originally always 

 sexual palpons. These latter have often a peculiar structure and may be distinguished 

 as gonopalpons. Those corrns of the Physonectaa which have ordinate cormidia usually 

 possess a constant number of palpons attached above the base of the siphon ; in those 

 corms, however, in which the cormidia are dissolved, usually very numerous palpons are 

 scattered along the whole trunk of the siphosome. 



[ZOOL. CHALL. EXP. PART LXXVII. — 1888.) Hhhh 25 



