17S MEDl'S.E OF THE WORLD. 



Ralhkta oclopunclala, GIARD, 1888, Bull. Sci. France Belg., ser. 3, annee I, p. 317, plate 21. CHUN, l896,Bronn's Thier-Reichs, 

 Bd. ^, Abth. l, p. 253, taf. 12 (development of medusa-buds). BEDOT, 1905, Revue Suisse de Zool., tome 13, p. 145 

 (all papers cited to 1850). 



\largtllium actopunctalum, BROWNE, 1903, Bergens Museums Aarbog, No. 4, p. 15; 1905, Proc. Royal. Soc. Edinburgh, vol. 25, 

 p. 755. 



Cubogasler gemmascens, HAECKEL, 1879, Syst. der Medusen, p. 76, taf. 6, figs. 8-[l (young budding medusa with only 2 mar- 

 ginal tentacles). 



Adult medusa. Bell pyriform,with solid, apical projection, and about 5 mm. in height and 

 4.5 mm. in diameter. Gelatinous substance thick at the apex of the bell, but thin upon sides of 

 bell-cavity. There are 8 clusters of marginal tentacles. 4 of these are radial and are situated 

 at the bases of the 4 radial-canals, and the 4 others are interradial and are situated 45 from the 

 radial clusters. In the fully-grown medusa there are usually about 4 or 5 tentacles in each 

 radial cluster, while the interradial clusters are each composed of not more than 3 tentacles. 

 When the medusa is not yet fully grown, however, there are normally 3 tentacles in both radial 

 and interradial clusters. Tentacle-bulbs large and swollen and filled with entodermal pigment- 

 granules. Velum well developed. There are 4 straight, narrow radial-canals. The manu- 

 brium is provided with a distinct peduncle which, however, does not extend more than one- 

 third of the distance from the inner apex of the bell-cavity to the velar opening. The gastric 

 portion of the manubrium is short and quadratic in cross-section. The mouth is surrounded 

 by 4 prominent lips. Each lip terminates in a pair of oral tentacles each of which ends in a 

 knob-shaped cluster of nematocysts. In addition to these there is also a pair of knob-shaped 

 clusters of nematocysts upon the sides ot each lip, centripetal to the terminal knobs. Medusa- 

 buds are developed upon the sides of the manubrium about the region ot the stomach. These 

 medusa-buds appear on interradially situated positions on the stomach-wall. According to 

 Chun (1895, Bibliotheca Zool., pp. 20, 21) the order of development of the medusa-buds 



follows a very definite law. The oldest buds appear nearest 

 the peduncle of the manubrium and the youngest are found 

 9 lower down nearer the oral tentacles. The accompanying dia- 



gram will serve to illustrate the law of succession in position 

 and in time ot the various buds upon the manubrium ( I ) being 

 the oldest bud and (16) the youngest (newest). 



The oldest buds are developed near the proximal base of 



the stomach, and the newest and youngest are found near the 



bases ot the oral tentacles. Even before they are set free the 



,0 young medusa? begin to develop buds on their stomach-walls, 



' and these secondary medusa-buds follow the same laws of 



time and place ot development as do the primary medusa-buds 



(see Chun, 1895, p. 23). Chun, 1895, showed that the medusa-buds were formed entirely from 

 the ectoderm ot the manubrium, the entoderm taking no part in their development. As the bud 

 becomes older, however, a connection is formed between its gastrovascular cavity and that of 

 the mother medusa. The developing medusa-bud has, at first, only 4 radial tentacles, one at 

 the base of each radial-canal. When set free, however, it possesses 16 tentacles: 4 clusters 

 each ot the 3 tentacles at the bases of the 4 radial-canals; and also 4 simple interradial ten- 

 tacles. The color of the entoderm of the manuhrium and tentacle-bulbs varies from brown- 

 green to black. 



This medusa is common in the north Atlantic, where it has been taken off the coasts of 

 Norway, Barents Sea, Helgoland, England, Ireland, Scotland, and New England. Fewkes 

 found it in Narragansett Bay, Rhode Island, and it is common on the southern coast of New 

 England in March. Browne records this species from Valencia Harbor, coast of Ireland. 

 Levinsen, 1893, found it oflFthe west coast of Greenland. I believe that future studies will show 

 that R. blumenbachu of the Black Sea is identical with R. octopunctata. The drawing of the 

 oral tentacles of R. blumenbachu in Rathke's memoir is evidently diagrammatic and probably 

 quite erroneous. R. blumenbachu appears to be merely an R. octopunrtata in an intermediate 

 stage of growth wherein it has 3 tentacles in each of its 8 marginal clusters. 



