REPORT ON THE DEEP-SEA MEDUSAE. 9 



branches are longest in the middle (up to 10 mm.), and gradually decrease in size towards 

 the ends of the radial canal; they are very short at both ends. The genitalia proceed 

 from their lower wall. The four genital glands (figs. 5, 6) seen from the subumbrellar 

 surface have the shape of broad elliptical or almost circular leaves, occupying the centre 

 of the radial canals from which they hang freely into the umbrella cavity (figs. 1,2). On 

 closer inspection it is shown that each gland forms a delicately-pinnated leaf, whose 

 20 to 30 pairs of pinnated branches are lamellae placed perpendicularly (s). The upper 

 edge of each lamella is connected with a transverse pinnated branch of the radial vessel, 

 whose lower (subumbral) wall forms a fold; the lower free edge of each lamella is 

 serrated or rather, split up into a number of finger-shaped points. The number of these 

 points is greatest (10 to 15) in the broadest lamellae in the middle of each gland, smallest 

 in the narrowest lamellae at the two ends of the genitalia. Each lamella is therefore, in 

 itself the half of a pinnated leaf, whose straight upper edge has grown to the transverse 

 branch of the radial canal, whilst the divided lower edge projects freely into the umbrella 

 cavity. 



Order III. TKACHOMEDUStE, Haeckel, I860. 



Craspedotae with auditory clubs, which sometimes stand freely on the umbrella margin, 

 and are sometimes enclosed in auditory vesicles, with endodermal otolite cells. Ocelli at 

 the basis of the tentacles usually wanting. Genitalia always in the course of the radial 

 canals. Number of the radial canals, sometimes four, sometimes six, sometimes eight, 

 never more ; between these there are often centripetal blind canals. The velum is firm 

 and broad. Ontogenesis, so far as we yet know, hypogenesis (or direct development 

 without alternation of generations) usually accompanied by metamorphosis. 



Family, Teaciynemidj:, Gegenbaur, 1856. 



Trachynemida;, Haeckel, System der Medusen, 1879, p. 255, taf. xvii. 



Trachomedusae with eight radial canals, along whose course the eight genitalia lie ; 

 with long tube-like stomach without ventral peduncle ; with auditory clubs, which are 

 seldom free but usually enclosed in auditory vesicles lying on the umbrella margin. 



Sub-family, Pectyllid.e, Haeckel, 1877. 



Trachynernula with sucking cups on the tentacles, with radial mesogonia or broad 

 mesenterial bands. 



(ZOOL. CHALL. EXP. PART XII. 1881.) M 2 



