HHI/nvniVli:. li.'l.'l 



the same thing in f .'<;<>/<,/>,<(. In C.n.\ wo/>,-i; \,im,i. h,ui,i R. P. Bigelow showed that the rhopalia 

 an- derived from every alternate tentacle of tin- so phostoma. the other tentacles degenerating 

 wholly. I find that in this medusa when the ihopalium regeneraics it gives rise to a short latcial 

 branch thus tending in an abortive manner to regenerate the tentacle, fim which it originally 

 came. 



Many observations have heen cairied our upon the emhi\o|i>gy of Rhi/.ostomae, and 

 reviews ot these researches will he found in the descriptions of Cassiopea xamachana, Cotvl- 

 orhiza tuberculata, Rhtzostoma pulm'i, Mastigiai /><;/>;/<;, Phyllorhiza f>iin<-tiit<i, and St'inm- 

 lnf>/iiis wi-lt-tivris. Clans. Goette, R. P. Bigclow, Kowalevsky. \oii Lendenfeld, and Vanhntfcn 

 have heen especially active in these it-searches. 



Haeckel, 1880, considered the presence or absence ot a unitarv, cruciform, genital cavity 

 to he of great systematic importance and sought to separate families upon this distinction; hut 

 Claus, von Lendenfield, Vanhotfen, Maas, and Browne have demonstrated that this is a matter 

 of no great import, tin in different individuals of ihe .same species we nun find in some cases 4 

 separate genital sacs, while others have a crucilmin genital cavity, and still others may have 

 a more or less complete coalescence and breaking apart of the partitions m some quadrants 

 and not in others. It is therefore evident, as was first clearly shown by Claus, 1883 (Oin.in- 

 isation und Entwick. Medusen), that the conditions exhibited by the genital sacs afford no 

 criteria for the distinction even of genera, much less of families. Indeed, Haeckel 's svstem 

 leads to the separation ot closely related forms and the close approximation of remotely 

 related forms, and is quite artificial. 



Claus, 1883, 1886, and Vanhiiffen, 1888, have attempted to separate the families of 

 Rhizostomae upon the distinctions afforded by the manner of branching of their mouth-arms. 

 Claus's system somewhat modified by von Lendenfeld, 1888 (Zeit. fur wissen. Xool., Bd. 47, 

 p. 208), distinguished nine families as follows: 



RmzovroM.t;: Scyphomedus.T without marginal trntaclrs and with 8 adnuli.il mouth-arms. 



Archirihizid.F: Mouth-arms unbranchcd. Gastrovascular network simple. No central mouth. 



Cassiopfitfa: Arm-disk flat. Arms long, irregularly branched with appendages. Radial-canals numerous. No central 

 mouth. 



Craunostoinldtf: Arm-disk wide, style-shaped, arms dichotomously forked. Arm-margins free, with clubs. Ccntn| - tl] 

 canals end blindly. Subgenital porticus unitary. Central mouth-opening present. 



CepheiiLt: Arm-disk wide and flat. Arms dichotomously forked, w ith 2 of the axial, terminal wings turned outwards. 

 VA "ith clubs. No direct central mouth-opening. 



LychnorhizliLr: Arms j-leaved or distally 3-winged. 8 or 1 6 radial-canals. Gastrovascular network simple. No central 

 mouth. 



StomolophitLf: Arm-disk style-shaped, elongate, with 8 pairs of lateral "shoulder ruffles" or "scapulets." Proximal 

 parts of the arms fused into a tube, distal parts branched. 16 radial-canals, with well-developed net-work of con- 

 necting vessels. No central mouth. 



RhizoslomnLr: Arm-disk style-shaped, elongate, with 8 pairs of lateral "scapulets" with clubs. Lower-arm three- 

 winged, with dorsal mouths. 16 radial-canals. Centripetal network of canals well-developed. X" u-ntr.il moulh. 



Caiosi\lidii: Arm-disk very wide, elongatei and style-shaped. Lower .irrn v^inged with dorsal mouths. Nocentrip- 

 etal networks uf canals. Subgenital porticus uniturv. No central mouth. 



Ltptobrachid*: Arm-disk wide and fused with the upper arms. Lower arms long, ribbon-shaped, and 3-winged. 

 Simple canal net spread over the entire subumbrella. Subgenital portitus unitary. No central mouth. 



A simpler system is proposed by VanhiiHen, iSS8 (Bibliotheca Zoologica, Heft 3), who 

 divides the Rhizostomte into 7 families: 



Rhizouomata sitnplicia: Mouth-arms Bimplc and unbranchcd. All of these are apocryphal, having been seen only 



hv Hactkel and I'Ywkrs. 



Dicholoma: M<iuth-arms dichotomously forked, with lateral expansion .. 

 Pinniita: Elongate mouth-arms pinnately or irregularly branched. 

 Triptera: Mouth-arms ^-winged. Each mouth-arm with a ventral and 2 dorsal lamella? which meet at a point at the 



lower end of the arm. 



Trigona: Identical with the Rhizostornata Irifttera. 

 Lorifera: Mouth-arms elongate, lash-like, and triangular in cross-section; with mouths developed along the 3 angles 



of the arms. 

 Xmfulaia: Mouth-arms with simitar-shaped "scapulets" or "ruffles" projecting from their dorsal sides. 



As was pointed out by Maas, 1903, Vanhoffen's Triptera and Trigona are identical 

 and should be united, thus reducing his families to six. Schultze, 1898, showed that the 

 mouth-arms of the " Dichotonni " of N'anhiiffen are not forked at their outer ends, but uive 

 rise to ^ broad, longitudinal, lutrnil lamella?, which may branch secondarily. With these 

 modifications Vanhoffen's system affords the readiest means of classifying the Rhizostomae, 

 being based upon the mutations of the most conspicuous organs, the mouth-arms. 



