42 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



ulothrix at the Tortugas. The entoderm of the proboscis and tentacle bulbs 

 is cream-colored, and the tips of the tentacles are turquoise. A single specimen 

 of this medusa was found at the Tortugas, Florida, on June 11, 1897, and 

 another in June, 1899. 



Bougainvillia niobe, Mayer. 



Bougainvillia niobe, Mayer, A. G., 1894, Bull. Mus. Comp. Zool. at Harvard Coll., 

 Vol. XXV. p. 236, Pi. I. Fig. 2. 



Specific Characters. — The bell is 6.75 mm. in height and 4.8 mm. broad. 

 The bell walls are thick and gelatinous. The marginal tentacles arise from 

 4 radially situated bulbous swellings, each one of which gives rise to 6-8 ten- 

 tacles. At the base of each tentacle, upon the inner or centripetal side, there 

 is a dark-colored pigment spot, or ocellus. This is an ectodermal structure, and 

 it projects slightly from the surface of the tentacle. The tentacles are not very 

 flexible and are about as long as the bell height. The velum is well developed. 

 There are 4 straight, narrow, radial tubes. The proboscis is wide, but not very 

 long, extending only about half the distance from the apex of the bell cavity 

 to the velar opening. There is a small peduncle. There are 4 large, radially 

 arranged bunches of oral tentacles. These arise as 4 main stems, each of which 

 branches dichotomously 4 times, thus giving rise to 16 tentacle tips from each 

 quadrant of the proboscis. These terminal tentacle tips are slightly knobbed, 

 and are composed chiefly of nematocyst cells. The tentacles of the proboscis 

 are very flexible and may be observed waving gracefully to and fro within the 

 cavity of the bell. 



The most remarkable characteristic of this species is the presence of numerous 

 medusa buds that arise from the gastric region of the proboscis. These budding 

 meduss are found in 8 radially arranged clusters situated near to and on 

 both sides of the places where the 4 radial tubes enter the gastric portion of the 

 proboscis. A study of sections of the proboscis of medusse killed in Flemming's 

 Chrome-Osmic- Acetic, and stained in Kleinenberg's 70% Alcoholic Hsematoxylin, 

 has shown that the proliferating medusce are formed entirely from the ectoderm, 

 the entoderm taking no part whatsoever in their formation. There is a very 

 well-defined lamella between the ectoderm and the entoderm of the proboscis 

 of the parent medusa, and the membrane of this lamella is never broken during 

 the time of the formation of the medusa bud from the ectoderm of the proboscis. 

 Indeed, the gastro-vascular cavity of the budding medusa is never connected 

 with that of the parent. The medusa buds develop very much as has been 

 demonstrated by Chun (1895 ; Bibliotheca Zoologica, Heft 19, Lfg. 1, p. 1-51, 

 Taf. I., II.; in Rathkea octopunctata, and Lizzia Claperedei ; excepting that 

 while in the forms studied by Chun the gastro-vascular cavity of the bud 

 finally acquires a connection with that of the parent, in Bougainvillia niobe no 

 such connection is ever formed. Chun concluded that medusa buds which are 

 derived entirely from ectoderm cannot be homologous with those that are 



