SYSTEMATIC AND BIOLOGICAL ACCOUNT 37 



I believe to belong to them. A similar stem was associated with many nectophores at one ' Manihine ' 

 Station in the Gulf of Aqaba. One of the eleven Indian Ocean Physonects, a new species (see p. 59) 

 is of special interest because of its apparent relationship with the one and only known high-arctic 

 Siphonophore Stephanomia orthocanna described by Kramp (1942). Kramp's species is characterized 

 by the straight lateral canals of the nectophores. In the Antarctic there is a third Physonect of this 

 group, also new, and the type species of a new genus which has been named (p. 55) after Mr J. W. S. 

 Marr. It has very characteristic bracts with truncated distal ends and straight lateral canals in the 

 nectophore. To this new genus both S. orthocanna and the two new species belong. 



Athorybiadae Huxley, 1859 

 Syn. Anthophysidae Brandt, 1835 

 Eschscholtz (1829) included in his genus Athorybia: (1) Rhizophysa heliantha Quoy & Gaimard; 

 (2) R. melo Quoy & Gaimard; and (3) Physsophora (sic) rosacea Forskal. Haeckel (1888a) took 

 Rhizophysa melo Quoy & Gaimard as the type of a new genus Melophysa. I now select Physsophora (sic) 

 rosacea Forskal as the type of Athorybia 1 Eschscholtz. I believe that Rhizophysa heliantha Quoy 

 & Gaimard is a synonym of Athorybia rosacea (Forskal). The two genera Athorybia and Melophysa 

 are quite distinct. In the latter a distinct nectosome is found. 



Schneider (1896, p. 590) suggested that Athorybia was really a sexually mature, larval (neotenous) 

 form, with which I agree. I go further in suggesting that Melophysa melo represents a form that has 

 similarly become sexually mature but at an early post-larval stage. This would account for the absence 

 of nectophores in Athorybia and the presence of a single functional nectophore at any one time (?) in 

 Melophysa. Furthermore, I consider an important point in this argument, to be the shape of the 

 nectophore in Melophysa. In Bigelow's (1931) fig. 217, I suggest that the nectophore has become 

 twisted through 180 , as so often happens, about one axis or the other, 2 even in a species like Diphyes 

 dispar. I believe that in Melophysa melo the pedicular canal ascends and does not descend to the 

 nectophore. Now the important point is that in young nectophores of Agalma okenii there is a very 

 distinct inferior pedicel, a condition which I believe to be homologous with that in Melophysa melo. 

 If Bigelow's nectophore were to be reversed, the loops of the lateral canal could also be homologized 

 with those of Agalmids. The external features of the nectophore are unlike those of other Agalmids as 

 my figures show (Text-fig. 7), a fact that once more suggests that Melophysa 1 ?, nectophore is a survival 

 of an earlier stage of development of these organs. 



Schneider (1896) gave no clue as to the identity of the form he was discussing except that it was 

 evidently the larval form described by Haeckel (1869a). The identity of Haeckel's larvae can only 

 be surmised. He took a unique specimen of Athorybia ocellata (syn. rosacea) at Lanzarote in 1876, 

 and the larvae, which he was observing and describing at the same time, probably came from this 

 same specimen. 



Athorybia Eschscholtz, 1829 

 Anthophysa Brandt, 1835. 



Angela Lesson, 1843. 



Athorybia Kolliker, 18536; Huxley, 1859; Gegenbaur, 1859; Fewkes, 1882; Haeckel, 18886; Fewkes, 18886. 



Ploeophysa Fewkes, 18886. 



Bigelow (193 1, p. 579) discussing Melophysa melo said, 'it will never be possible to settle conclusively whether or not it 

 was this same form Athorybia rosacea [Bigelow, syn. Melophysa melo Q. & G.] that Forskal described and pictured as 

 Physsophora (sic) rosacea, for his figures and account would apply equally to any Athorybia'. But, as Haeckel says, Forskal 

 was describing a typical Mediterranean form, which Melophysa melo is not. 



I have even witnessed in Agalma elegans the loss of one of a series of nectophores, shot off when the stem contracted, 

 followed by the twisting round of a neighbouring nectophore to take its place. 



