TURRITOPSIS. 167 



carried out in a very different direction in the genital pouches on the 

 pendent proboscis of Stomotoca. 



Massachusetts Bay, Nahant (A. Agassiz). 



Cat. No. 274, Nahant, Mass., May 12, 1862, A. Agassiz. 



TURRITOPSIS McCR. 



Turritopsis McCR. Gymnoph. Charleston Harbor, p. 24. 1857. 

 Turritopsis McCR. On Turritopsis, new species, .... p. 2. 1856. 

 Turritopsis AGASS. Cont. Nat. Hist. U. S., IV. p. 347. 1862. 



Turritopsis nutricula 



Turritopsis nutricula McCn. Gymn. Charleston Harbor, p. 25, Pis. 4, 5, 8, Fig. 1. 

 Turritopsis nutricula AGASS. Cont. Nat. Hist. U. S., IV. p. 347. 1862. 

 Turritopsis nutricula A. AGASS. ; in Proc. Boston Soc. Nat. Hist., IX. Figs. 22, 23. 



The young Medusae have only four stiff tentacles, with a long bottle- 

 shaped digestive trunk (Fig. 269), fastened by its base to the lower 

 part of a short prolongation of the bell, along rig. 259. 



w r hich the chymiferous tubes run ; the digestive 

 cavity has four marked prolongations, surmounted 

 by bunches of lasso-cells ; along the upper part 

 of the digestive cavity, the genital organs are 

 developed in four bunches, placed along the pro- 

 longations of the actinostome. As the Medusae increase in size, there 

 are four more tentacles formed, one in the middle of the space between 

 the chymiferous tubes ; the genital organs increase in length, and by 

 the time two additional tentacles (3, Fig. 270) have been formed, one 

 on each side of the tentacles of the second cycle, the genital glands 

 have become very much swollen, and occupy nearly the whole length 

 of the digestive cavity and proboscis. With Fig. 270. 



advancing size the gelatinous mass loses its 

 bell shape, and becomes more globular, the 

 tentacles (then sixteen in number) losing 

 somewhat their stiffness ; when it has only 

 four tentacles, the young Medusa resembles 

 so much Sarsia, in the shape of the bell and 

 of the digestive cavity, that were it not that 

 Sarsia carries its tentacles curled up close to the circular tube, while 

 in Turritopsis they stand stiffly out from the rim of the bell, like the 

 tentacles of Eudendrium, it would be difficult to distinguish them apart. 

 Not having traced this Medusa beyond the stage when it had sixteen 



Fig. 269. Young Turritopsis nutricula, with four marginal tentacles ; greatly magnified. 

 Fig. 270. Somewhat more advanced Turritopsis, having sixteen tentacles. 



