504 MEDUSA OF THE WORLD. 



Order CARYBDEIDiE Gegenbaur, 1856. 



Carybdtida, Gegenbaur, 1856, Zcit. fur wissen. Zool., Bd. S, p. 214. 



CharyhJta, CtAUS, 1886, Arbeit. Zool. Inst. Univ. Wicn, Bd. 7, p. no.— VANHiirrtN, 1892, Ergcb. dcr Plankton Eipcdition, 



Bd. 2, K. d., p. 21. 

 Mtirsupialida, Acassiz, L., 1862, Cont. Nat. Hist. U. S., vol. 4, p. 174. 

 Cubomtdusii, Haeckel, 1880, Syst. dcr Mcduscn, p. 42J.— Goette, 1887, Abhandl. zur Entwickclungsgcsch. dcr Thicrc, p. 66, 



Ix:ipzig.— ScHWEiKorr, 1889, Morphol. Jahirb., BJ. 15, p. 25.— Co.sant, 1898, Mem. Johns Hopkins Univ. Biol. Lab., 



vol. 4, No. I, p. 3.— Haacke, 1S87, Jcnaische Zeitschrift, Bd. 20, p. 590.— Maas, 1907, Ergcb. und Fortschrittc dcr Zool., 



Bd. I, p. 197. 



CHARACTERS OF THE ORDER. 



Scvphomedusae with 4 perradial, knob-shaped, marginal sense-organs which are situated 

 within niches upon the sides of the bell. Each sense-organ contains an entodcrnial concretion, 

 and one or more ectodermal ocelli. There are 4 interradial tentacles or groups of tentacles. 

 4 wide perradial sacs extend outward from the central stomach into the interstitial space of the 

 bell. These sacs are incompletely separated one from another by 4 narrow interradial septa. 

 There are 8 gonads each one of which is leaf-shaped and attached along one side to an inter- 

 radial septum, from which it extends outward into the gastrovascular space of the bell. The 

 bell-margin is not cleft into lappets. The subumbrella forms an annular diaphragm called 

 the velarium which partially closes the opening of the bell-cavity. 



The perradial sense-organs in the Car\bdeidie are knob-shaped, and are set within 

 niches upon the sides of the bell. The stalk of each knob is hollow and connected with the 

 gastrovascular system of the bell. The knobbed end of each club contains a large entodermal 

 concretion and one or more ectodermal eyes (plate 56, fig. 6"). These eyes are placed on 

 the inner or centripetal side of the club and look inward into the bell-cavity. The larger 

 eyes are provided with a doubly convex lens, back of which is a cup-shaped space occupied 

 by the lens-capsule and the retina. The retina is made up of a single la\er of cells forming a 

 hollow cup, into which the lens with its capsule fits. The central space of the retinal cup 

 is clear and glassy. This transparent region is enveloped by a deeply pigmented part and 

 back of this lies a muscular zone. The retina is made up of three kinds ot cells, some long 

 and prism-shaped, others short and pyramidal, and still others long and pyramidal. The 

 deep-lying ends of these cells are more or less pigmented, while their outer parts are trans- 

 parent, and being packed closely together, they form the vitreous center of the retinal cup. 

 (See Conant, 1898; Berger, 1900; etc.) 



The tentacles of the Car\bdeidae are interradial and arise at a level slightlv above the 

 apparent bell-margin, although they are actualU' structures of the subumbrella. Their proxi- 

 mal parts are developed into tough, gelatinous, wing-shaped or spatula-shaped structures 

 (pedalia), which probably serve as keels to steer the animal in its course through the water. 

 The long, distal ends of the tentacles are cylindrical and highly contractile, and their outer 

 surface is covered with rings of nematocysts. The tentacles are hollow and their lumen is 

 connected with the gastrovascular space of the bell. This is accomplished by the interradial 

 septa being incomplete near the bases of the tentacles and thus the lumen of each tentacle 

 is placed in direct connection with the gastrovascular spaces of the two adjacent perradial 

 pouches. The flexible pans of the tentacles are armed with nematocysts, the stinging power 

 of which is so great that the name "Sea Wasp" is commonly given to these medusx. 



The velarium is an annular membrane which extends inward from the bell-margin, 

 forming a diaphragm which partially closes the cavity of the subumbrella; superficially it 

 bears a close resemblance to the velum of the Hydromedusx, but is separated from the exum- 

 brella by means of a continuous sheet of entodermal tissue which penetrates the gelatinous 

 substance of the bell all around the hell-margin, and connects the entoderm o( the intermediate 

 lamella with the ectoderm of the outer surface of the bell. It thus forms a ring ol entoderm 

 around the bell-margin which completely separates the ectoderm of the subumbrella side of 

 the velarium from that of the exumbrella. ,\t points other than those occupied by sense- 

 organs or tentacles this vascular, entodermal lamella forms a simple, flat sheet, but when it 

 comes to the tentacle-bases, or sense-organs, it makes a loop upward over them. Thus the 

 tentacles and sense-dubs are structures of the subumbrella only, for they lie below the ento- 

 dermal lamella which isolates them completely from the exumbrella. What the philogenetic 

 significance of this lamella may be we do not know, and until this is discovered we can not be 

 certain that the velarium of the Carybdeidae is not strictly homologous with the velum of the 



