BAHAMA MEDUSA. 11 



mentary tentacle-bulbs. This is one of the most abundant medusae at the 

 Bahamas in summer. 



Bougainvillia Niobe, Mater. 



Figs. U-lBc, Plate II. 



Mater, A. G., 1894 ; BuU. Mus. Comp. ZoOl. at Harvard Coll., Vol. XXV, p. 336, PI. I, Fig. 2; 

 Ibid. Vol. XXXVII, p. 43. 



Adult Medusa, Fig. 14. Bell 6.75 mm. high and 4.8 mm. in diameter, with 

 vertical sides and thick gelatinous walls. Four radially situated clusters of 

 marginal tentacles, each composed of about eight tentacles about as long as 

 the bell height. On the lower side of each tentacle near the bulbous base 

 there is a dark-colored ocellus. Four straight, narrow, radial canals. Manu- 

 brium wide, flask-shaped, and cruciform in cross section. About one-half as 

 long as the height of the bell-cavity. Four radially situated clusters of oral 

 tentacles, each of which branches dichotomously four times. These are very 

 flexible, and their distal ends are knobbed. 



Medusa buds arise from the eight adradii of the manubrium ( Fig. 15 ) ; the 

 youngest buds being immediately under and on both sides of the point of 

 entrance of each radial canal, while older ones are found farther down the 

 sides of the manubrium. The youngest buds (Fig. 15% Plate II) were small 

 ovoid vesicles contained entirely in the ectoderm. The limiting membrane, si, 

 between the entoderm and ectoderm of the manubrium, in the neighborhood 

 of these buds, was entire, and I could find no evidence of cells passing through 

 it. Indeed, throughout the future development of the buds the entoderm re: 

 mained inert and its limiting membrane unbroken. The wall of the vesicle 

 consisted of two layers of cells; an outer epithelium of ectodermal cells, 

 e G t. h., destined to give rise to the ectoderm of the bud, and an inner layer 

 of somewhat larger cells destined to give rise to the entoderm of the budding 

 medusa, e n t. h., Fig 15^. These latter cells, it will be observed, are entirely 

 encased by the ectoderm of the manubrium. They may, however, have been 

 derived at an earlier stage from the entoderm, and have migrated into the 

 ectoderm. Careful search has, however, failed to reveal evidence of any such 

 migration, and in default of evidence to the contrary, we assume that these 

 cells may be ectodermal in origin, although destined to produce the entoderm 

 of the bud. 



The central cavity of the vesicle is partially filled with a loose mass of 



