20 DISCOVERY REPORTS 



by using what seems to be a faulty nomenclature — one that leads to a confusion of identities. He said 

 much about two not very well-known Physonects which, like Bigelow, he called ' Anthophysa' and 

 ' Athorybia '. The proper names of these two forms are Athorybia Forskal (for Garstang's ' Anthophysa ') 

 and Melophysa (Haeckel) (for Garstang's 'Athorybia '). The synonymies are explained in my systematic 

 notes (p. 37). It is most unfortunate that these corrections must be made, since Garstang's paper 

 will become a classic. But in places Garstang uses both names Athorybia and ' Anthophysa ' for one and 

 the same animal, Athorybia rosacea Forskal: at other times he uses one of these names 'Athorybia' 

 for a distinct species Melophysa melo (Haeckel). The confusion in siphonophore synonymy is 

 notorious. 



According to Garstang's theory the rudimentary medusoid buds, discovered by Chun in ' Athorybia ' 

 {^Melophysa Haeckel) and hitherto regarded as vestigial nectocalyces, are (bearing Pelagohydra in 

 mind) tentatively claimed as obsolescent hydroid gonophores ; in other families they are said to have 

 been converted into nectocalyces; and in 'Anthophysa' ( = Athorybia Forskal) they are thought to have 

 disappeared altogether. I have now collected and examined quite a number of these Melophysa 

 nectophores (see Text-fig. 7). They may be more primitive in many ways than other nectophores, 

 but show no obvious sign of being obsolescent gonophores, nor of being vestigial. In fact ' Anthophysa ' 

 ( = Athorybia Forskal) may never have possessed nectophores at all, being descended from an 

 'Athorybia larva '-like ancestor comparable with the stage in the ontogeny of an 'Athorybia larva' 1 

 before nectophores arise. In that case Athorybia would be neotenous. Garstang's 'Athorybia' 

 ( = Melophysa Haeckel) is in my opinion another neotenous form descended from a similar 'Athorybia 

 larva '-like ancestor, only it is comparable with a rather later stage in the ontogeny of an ' Athorybia 

 larva' when nectophores have begun to develop. But of course we cannot be sure whether or not an 

 'Athorybia larva' represents an actinuloid larva with precocious gonophore (nectophore) buds. Even 

 if it does it is probable that Garstang's ' Anthophysa ' ( = Athorybia Forskal) arose at a stage in phylogeny 

 before the appearance of the precocious buds which, in Garstang's theory, represent the obsolescent 

 hydroid gonophores. Garstang tried to clinch his argument by saying that the nectocalyces of the 

 nectosome of Physonects must represent the gonophores of pre-siphonophore (i.e. hydroid) ancestors 

 because they are produced from the oozooid, which in Siphonophores remains sterile, whilst sexual 

 siphonophore medusa buds are borne on secondarily budded gonopalpons. 



The explanation of the fact that nectophores (sterile swimming medusae) arise from the oozooid is, 

 I believe, that they were evolved later than the bud-borne, sexual medusae distributed along the stem 

 of all Physonects, that they were developed precociously in the larvae of Physonects purely for 

 swimming purposes, and were then further developed and carried into adult life — a curious case of 

 adult retention of an organ that was originally transformed and developed precociously for larval 

 use. That a medusoid gonophore bearing a sexual manubrium can lose this manubrium and be 

 specially developed for swimming is proved by the transformation of gonophores into special swimming 

 nectophores in the eudoxids of forms like Diphyes dispar, D. bojani and D. chamissonis. 



LARVAL AND DEFINITIVE NECTOPHORES 

 From a study of the ontogenies of many calycophore species of the genera Rosacea, Hippopodius, Vogtia, 

 Chelophyes, Muggiaea and Galetta, we can deduce that as successive nectophores are budded off, so 

 in the course of evolution they have become more and more specialized. For instance, the second 

 definitive or adult (posterior or inferior) nectophore of Chelophyes appendiculata is very unlike the 

 first definitive one, which replaces the original, caducous larval one. This type of ontogeny is typical 



1 The expression 'Athorybia larva' is used, not for the larva of Athorybia rosacea, but for the larvae of Physonects like 

 Agalma spp., at the stage when they look rather like miniature specimens of A. rosacea. 



