MUSEUM OF COMPARATIVE ZOOLOGY. 135 



always remain problematical, and there is no good reason to identify the 

 form studied by Huxley with it. 



In the Grundziige der Zoologie, 3 Auf , p. 237, Claus includes in the 

 family of Agalmidse Forskalia {^Stephanomia, M. E,), Halistemma., and 

 Agalmopsis. He, like .Haeckel, mentions Nanomia cava as a species of 

 Halistemma, and says that Stephanomia (Peron) is included in the same 

 genus. Packard follows Claus in this reference of Nanomia to Hali- 

 stemma. 



In Nanomia cava, the first formed structure in the larva, according to 

 Mr. Alex. Agassiz, is the float, as in Agalmopsis {Stephanomia, Metsch.). 

 In Halistemma, according to MetschnikofF, the swimming-bell and float 

 develop together from the very first. Although it is possible that the 

 float is simply a modified Medusa bell or nectocalyx, no one would mis- 

 take the young of Halistemma for that of a Nanomia larva. As Metschni- 

 koff has already pointed out, Nanomia in its younger stages resembles 

 the ^Qxwx's Agalmopsis* {Stephanomia, Metsch.). Huxley's classification 

 of the Siphonophorse, with a verbal change, is the best which has been 

 proposed as far as the Agalmid£e are concerned. We can retain the 

 three generic names Agalma, Agalmopsis, and Halistemma. That would 

 keep Eschscholtz's genus to designate ^ Physophorid with a trifid tentacu- 

 lar knob, the Agalmopsis of Sars with a single terminal filament on the 

 same structure, and Halistemma, a form the tentacular knobs of which 

 do not have involucra, and the tentacle is replaced by the pedicels of the 

 tentacular knobs. In addition to the genera Agalma, Agalmopsis, and 

 Halistemma, I would include Athoryhia among the Agalmidee, on account 

 of its embryonic likeness to Agalma. It may possibly be simply the 

 young of this genus. The only other Physophorid, except Stephanomia 

 {Forskalia), where we have a multiserial necto-stem, is Physophora tetra- 



* Notwithstanding Sars figures three radically different kinds of knobs in his 

 genus Agalmopsis, a condition only observed, with this exception, in Rhizophysa and 

 the larval forms of certain Agalmidse, his figures 5, 6, on Plate V. are among the 

 earliest, if not the first, representations of a tentacular knob with an involucrum and 

 a single terminal filament. I retain, therefore, the name which he has given for the 

 Jelly-fish w^ith this characteristic, particularly on account of the exact use of Stepha- 

 nomia by Milne-Edwards (Ann. d. Sci. Nat. 1841, Tom. XVL p. 217). See also 

 Leuckart's note, Siphonophoren von Nizza, p. 93 ; and Huxley, Oceanic Hydrozoa ; 

 Sars, Fauna Littoralis Norvegioe, 1846. In Middelhavet's Littoral Fauna, where 

 all descriptions of Siphonophores are simply numbered, and with no subdivision, 

 Agalma ruhrum {A. punctatum, KolL) is followed directly by Agalma Sarsii, a 

 species with a trifid tentacular knob. In that work Sars makes no mention of the 

 genus with a covered (by an involucrum) tentacular knob and a single terminal 

 filament. 



