12 DISCOVERY REPORTS 



25° S, 47° 51' W, by Vannucci {igsiap. 78, 1951/; pp. iii, 114, 116). Only very young stages were 

 observed, less than i mm. in diameter; accordingly, the identification seems uncertain; they may be 

 young specimens of B. platygaster} The most recent description of B. carolinensis was given by Mayer 

 (1910, p. 165, PI. 16, figs. 7-9, PL 17, fig. 7). This is a small medusa, 4 mm. in height. The gonads 

 are interradial as in B. platygaster, but the manubrium is long and narrow, and the oral tentacles have 

 a long, undivided shaft. An identity between these two species therefore seems excluded. Recently 

 also recorded from the Gulf of Guinea (Kramp 1955, p. 249). 



B. fulva Agassiz & Mayer 1899 is an Indo-Pacific species. In size and general appearance it is very 

 similar to B. platygaster, but the stomach is usually longer, about half as long as the height of the bell- 

 cavity, though sometimes shorter (Maas 1905, PI. I, fig. 8). In young specimens the stomach may be 

 quadrangular (Maas 1905, PI. II, figs. 100, b), but in mature specimens the gonads are distinctly 

 adradial, and widely separated in the interradii (Maas 1905, PI. II, fig. 10c; Kramp 1928, text- 

 fig. 21). In this respect the species differs from B. platygaster. Though numerous specimens have 

 been examined by several authors, budding has never been observed. 



B. niobe Mayer 1894 occurs off the southern Atlantic coast of North America, from Chesapeake 

 Bay to Florida, and round Bermuda and the Bahama Islands. As mentioned above, the records from 

 the waters off the Brazilian coast are probably all referable to B. platygaster. B. niobe was well 

 described and figured by Mayer (1910, p. 166, PI. 18, figs. 1-3, text-fig. 90) and was re-examined by 

 Bigelow (1918, p. 368 and 1938, p. 104). In this species also the stomach is about half as long as the 

 height of the bell-cavity, and the gonads are distinctly adradial. This is especially emphasized by 

 Bigelow, who pointed out the almost complete agreement between B. niobe and B. fulva ; the only 

 difference seems to be the ability of the former to produce medusa buds, which have never been 

 seen in B. fulva. Mayer's figures show that B. niobe differs further from platygaster in the branching 

 of the oral tentacles, which have a fairly long, unbranched, basal trunk before the first bifurcation, 

 whereas in B. platygaster they bifurcate immediately after they issue from the mouth tube. Moreover, 

 the ocelli of B. niobe seem to be round, not crescent-shaped as in platygaster. The medusa buds of 

 B. niobe are developed directly on the lateral sides of the stomach, not in clusters. 



Thus B. fulva and B. niobe differ from B. platygaster mainly in the distinctly adradial position of 

 their gonads and in the length of the manubrium. Even if the flat shape of the stomach should be 

 due to contraction during preservation, it would be a remarkable coincidence if all the thirty-three 

 specimens collected by ' Discovery II ' showed in every case the same mode and degree of contraction. 

 I have come to the conclusion that Bougainvillia platygaster is a species distinct from B. fulva and 

 B. niobe. 



Asexual propagation in Bougainvillia platygaster 



Asexual budding was observed in twelve of the specimens of Bougainvillia platygaster collected by 

 ' Discovery II '. It should at once be emphasized that all the specimens were immature. In the largest 

 medusa buds, four long marginal tentacles can be seen curled or doubled up inside the umbrella-cavity 

 and the manubrium carries four small, simple oral tentacles, each with a terminal cluster of nemato- 

 cysts (PI. Ill, figs. 5 and 6). Apparently the buds are produced in three different ways: (i) from 

 pedicels of polypoid hydranths issuing from the corners of the manubrium of the medusa, (2) as 

 outgrowths from stolonial structures, and (3) directly from the walls of the stomach, but investigation 

 shows that there is no fundamental difference between them. 



(i) The first method is unique so far among the Hydromedusae. It is seen in five specimens, 

 5-6 mm. wide, from the south and east coasts of Africa (Stations 1374, 1375 and 1581), and it also 



1 After the above was printed I met Dr M. Vannucci who told me that B. carolinensis actually occurs off the east coast 

 of Brazil. 



