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



tubulis pluribus obsitus. Tubuli squarnis cartilagineis obtecti. Pars corporis nutritoria 

 cavitate natatoria interna, extrorsum se aperiente instructa," He distinguished four 

 different species, the fourth of which, Diphyes appendiculata, from the Pacific Ocean, is 

 here retained as the representative type of the genus (1, p. 138, Taf. xii. fig. 7). Nearly 

 allied to this are two Mediterranean species, Diphyes acuminata of Leuckart (5), and 

 Diphyes sieboldii of Kolliker (4). A third Mediterranean species is Diphyes subtilis of 

 Chun (87). Different from these is Diphyes elongata, Hyndman, from the northern 

 Atlantic (64), and an Indian species, Diphyes gracilis. Huxley united all these species 

 under the name Diphyes appendiculata; there seem to be, however, constant differ- 

 ences between these species, which may be considered as specific, the more so as they are 

 inhabitants of widely distant seas. A more accurate distinction is required. 



Gegenbaur, in 1859, distinguished not less than ten different species of the genus 

 Diphyes (10, p. 50) ; the majority of these belong, however, to other genera of Dipkyidas, 

 Diphyopsis {Diphyes campanulifera, &c), and Galeolaria (Epibidia quadrivalvis, &c). 



The cormidia of Diphyes (in the sense here restricted) possess a spathiform or three- 

 sided pyramidal bract, with a deep ventral fissure, and become mature as free Eudoxise 

 belonging to the genus Cucullus (compare above, Genus 12). 



Genus 28. Diphyopsis, 1 Haeckel, 1888. 

 Diphyopsis, Hkl., System der Siphonophoren, p. 35. 



Definition. — Diphyidse with two angular, slenderly pyramidal nectophores of similar 

 form and subequal size, one placed behind the other. First nectophore with a conical 

 or campanulate hydroecium. Each cormidium with a special nectophore (free as Erssea, 

 Genus 17b). Bracts pyramidal, conical or spathiform, with a pointed apex. Phyllocyst 

 simple, ovate, without radial canals. 



The genus Diphyopsis comprises those Diphyidse hitherto described as Diphyes, 

 which differ from the true Diphyes in the possession of numerous special nectophores, 

 each of which is the locomotive organ of a cormidium, swimming free as Erssea (compare 

 above, Genus 17). Diphyopsis bears the same relation to Diphyes that Lilyopsis has to 

 Praya. The special nectophore of each cormidium (wanting in Diphyes) is the originally 

 first gonophore, which has lost its sexual function, and produces no manubrium ; it is 

 subservient only to locomotion. 



The first described species of Diphyopsis is Diphyes dispar of Chamisso and Eysen- 

 hardt, inhabiting the Tropical and Southern Pacific (16, p. 365, Tab. xxxiii. fig. 4). A 

 very accurate description of it was given by Huxley (9, p. 30, pi. i. fig. 1). Probably 

 identical with it is Diphyes angustata of Eschscholtz. The Challenger collection con- 



1 Biphyopds = Similar to Diphyes. 



