188 THE MEDUSAE. 



Z. gemviosa McCrady, except that the exumbral nettle ridges are rather 

 longer. This slight difference seems hardly sufficient to warrant specific 

 separation, especially inasmuch as the specimens were not examined until 

 after preservation. It would be most interesting to know the relation of 

 the present medusae to the hydroid stage described from Juan Fernan- 

 dez by Hartlaub under the name of Z. nitida; it is possible that the two 

 Pacific forms may prove to represent but one species. 



Zanclea gemmosa McCrady. 



Zanclea gemmosa McCrady, '57, p. 151, pi. 8, figs. 4i 5. 



Gemmaria gemmosa McCrady, '57, p. 151 ; A. Agassiz, '65, p. 184, fig. 306; Mayer, : 00'', 

 p. 35, pi. 41, tigs. 137, 138. 



Plate 7, Fig. 3; Plate 44, Figs. 1, 2. 



Acapulco Harbor ; surface ; 5 specimens. 



The largest specimen is 1 mm. in diameter. 



As in Atlantic specimens the gelatinous substance is thin and the bell 

 rounded, an outline very different from that of Z. clado'phora A. Agassiz, 

 in which the gelatinous substance is thick. There are two stout perradial 

 tentacles, and alternating with them there are two small tentacular knobs. 

 Since these latter structures are very rudimentary in all the specimens, 

 although several have mature gonads, it is probable that they do not 

 develop into tentacles. In the contracted condition of the tentacles it is 

 impossible to distinguish the normal form of the nematocyst batteries or 

 cnidoblasts, which are closely crowded along their aboral sides (PI. 44, 

 fig. i), or to determine the extent to which their fibrils are extensible. 



The manubrium is sac-like, hanging about to the opening of the bell 

 when extended; the mouth is surrounded by a simple circular lip (PI. 44, 

 fig. 2\ 



The gonads are probably primarily interradial, as in other members of 

 the genus (Vanhiiffen, '89; Hartlaub, :07); but in the female the eggs 

 grow so large that they obscure this arrangement, and finally come to 

 occupy the entire wall of the manubrium (PI. 44, fig. 2). In the male the 

 location of the sexual products seems to remain permanently interradial. 



Color. — The manubrium and the swollen bases of the tentacles are 

 salmon pink. 



