MKDL'S.E <>K WOODS H<»LK REGION. •_".» 



characterized 1 ■>■ an active habit and quick vigorous movements lacking in many of the other orders. 

 Sensory organs when present are on the bases of the tentacles as pigmented, ocellate structures, prob- 

 ably visual in function. Otocysts arc entirely lacking in this order. The radial canals are usually four 

 in number, rarely six or eight. Gonads are developed and borne on the walls of the manubrium, 

 rarely extending somewhat upon the proximal portions of the radial canals. — X, moping. 



II. I.ki'tomkih's.f.. — Compared with the Anthomedusae the umbrella of medusse of this order is 

 usually tlat and disk-like: velum smaller and more delicate, at times difficult to distinguish, so that 

 in many of the species motion is somewhaf sluggish, being produced as much through the general 

 contraction of the umbrella as by the velum. Sensory organs, when present, are usually otocysts, 

 rarely ocelli, more rarely both, or both may he lacking. Otocysts are usually borne between the bases 

 of tentacles, sometimes upon the inner side of their liases, and are probably equilibrium organs rather 

 than visual. Gonads are borne along the line of the radial canals, rarely extending to the manubrium 

 and upon its sides. — Timu, Nemopsis. 



III. TiivcnoMEncs.K. — Usually devoid of a polyp stage, though the recent determination of this 

 in Gonionemus, by Perkins, suggests the possibility of its occurrence in others. Sensory organs, when 

 present, are otocysts, entoderms] in their origin, ocelli usually lacking. Gonads borne upon the 

 subumbrellar surface of the radial canals, often throughout their entire length. Umbrella usually 

 hemispherical or bell-shaped; marginal tentacles usually numerous. 



IV. Xakc omeihs-J-:. — Somewhat flattish, or disk-shaped umbrella, with tentacles set in socket-like 

 receptacles high on the exumbrellar surface; radial canals usually in the form of tlat. pouch-like 

 diverticula of the stomach. 



V. Siphoxophora. — Comprising free-swimming polymorphic colonies, which are produced by 

 budding from a medusoid individual. Gonads produced in specialized medusoid gonophores which 

 seldom become free from the colony. The Siphonophora are characterized by an extreme degree of 

 specialization found nowhere else among the coelenterates, so great indeed as to leave some doubt as 

 to the homologies of some of the individuals. • 



ANTHOMEDUS/E. 



( oiioniid.k. — Manubrium cylindrical; mouth simple, devoid of lobes or tentacles; gonads borne 

 on the manubrium, but not radially divided; radial canals four, narrow; marginal tentacles lour. 

 unbranched. 



Tiarid.e. — Manubrium quadrangular; mouth with four lobes, simple or fimbriated; gonads four 

 or eight, radially disposed upon the manubrium; radial canals four, rather wide; marginal tentacles 

 unbranchi d. 



MargelidjE. — Manubrium quadrangular, mouth usually simple or with four plain lip-like lobes, 

 and with four or more simple or branched oral tentacles; gonads four or eight, borne on the manubrium ; 

 radial canals four, usually narrow; marginal tentacles unbranched. 



Cladonemidje. — Manubrium usually quadrangular, mouth rarely simple, usually provided with 

 oral lol.es or tentacles; radial canals narrow: marginal tentacles variously leathered or branched. 



I'.imih CODONHDjE. 



Kl:\ TO I UK GENERA. 



A. With two or four marginal tentacles, equallj developed. 



1. Ten in c]i'- and manubrium long, the latter extending far beyond the velum: bell hemispheric!) I Syiicorync 



■2. Tentacles rather short and stent, capitate ends, manubrium with one or more constrictions, sometimi 



extending slightly beyond the velum; bell ofien deal Dipun no 



;i. Tentacles as in preceding, I mt clavate, and with a distinct ring of nematocysts between the base ami 



club-like ends; bell rather high ami with rounded projection Dipurdla 



I. Tentacles closely coiled in swimming; lie II high and with eight rows of nematocysts Ectopleura 



5. Tentacles only i\\" at liberation, four in maturity; bell oval or hemispherical, ii* surface dotted with 



nematocysts HydriclUhys 



G. Tentacles rudimentary; bell elongate, oval Pt nnaria 



7. Tentacles only two; bell hemispherical ami with rouuded apical projection /'- riffonimus 



