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



They arise partly from the pedicles of the cormidia, partly from the branches of the 

 gonodendra ; it may be that many of the former (or perhaps all ?) are young siphons, 

 which afterwards get a mouth-opening. Those which arise constantly from the branches 

 of the gonodendra may be distinguished as gonopalpons (fig. 8, q). The second kind of 

 palpon is connected with the tentacles, so that always a single tentacle (fig. 6, t) arises 

 from a common pedicle with a single palpon (fig. 6, to). These tentacular palpons are 

 simple, very contractile, cylindrical tubes, closed at the pointed distal end, whilst their 

 proximal end opens into the common pedicle ; they do not possess the hepatic villi of 

 the first kind. Eschscholtz even compared them with the ampullae of the ambulacral 

 feet in Echinoderms (1, p. 158) ; Leuckart calls them " Tentakel-Blascken " (81, p. 197), 

 and Huxley describes them as basal sacs (9, p. 103). The physiological function of these 

 basal ampullae is, indeed, the same as those of the ambulacral ampullae in the 

 Echinoderms. The morphological value, however, is very difficult to make out. It may 

 be that they are only secondary organs developed from the base of the tentacles, which 

 originally belong to the siphons. On the other hand it is possible that originally a pair 

 of siphons has arisen from a common pedicle ; the first siphon has lost the tentacle and 

 preserved the hepatic villi and the mouth ; the second siphon, on the other hand, has 

 lost the latter organs and preserved the tentacle. The incipient basal ampulla (fig. 

 7, to) is much larger than the young tentacle arising from its base (t). 



Tentacles (figs. 1, 3, 6, t). — The long tentacles exhibit in all Physalidse the same 

 structure, accurately described by Huxley (9, p. 103, pi. x. figs. 11, 12). They are 

 slender moniliform filaments, or rather ribbon-shaped tubes, and agree essentially with 

 those of Salacia (PI. XXV. fig. 5, t). Only the primary tentacle (fig. 1, t) arises 

 directlv from the base of the protosiphon ; all the other (secondary) tentacles arise from 

 a common pedicle with a siphon and a palpon (fig. 6) ; or more correctly speaking, the 

 tentacle (t) and the tentacular palpon (to), closely united, have a common pedicle, which 

 arises from the same stalk of the cormidium as the siphon. As stated above, the palpon 

 (the basal sac or basal ampulla, to) bears to the tentacle the same physiological relation 

 as the ambulacral ampulke of Echinoderms to their feet. In form and structure the 

 numerous slender accessory tentacles are the same as the single large main tentacle, which 

 arises from the middle of the ventral group and surpasses the former ten to twenty times 

 in thickness ; its breadth reaches 3 to 6 mm. or more. Its length is usually more than 

 a metre, but it may reach in the expanded state ten to twenty metres or even more, as 

 in Caravella maxima. The ventral side of each tentacle bears a muscular suspensorium 

 (similar to a ribbon-shaped mesentery), whilst the dorsal side is beset with a series of 

 very numerous reniform cnidonodes. Each of the latter may .be regarded as a kidney- 

 shaped tentillum or lateral branch, since it contains a diverticulum of the tentacular canal. 

 The thick dorsal wall of this cavity is filled with innumerable spherical cnidocysts. 



Gonodendra (PI. XXVI, figs. 3, G, g, 8). — The corms of all Physalidas are monoecious 



