76 MEDUSAE OF THE WORLD. 



2 or 3 ring-like gonads girdle the manubrium. The two upper gonads are short, the 

 uppermost one being near the middle of the manubrium, and the next lower separated from it 

 by a short interval. The lowermost (distal) gonad is about twice as long as either of the others, 

 and it is adjacent to and above the stomach. 



The entoderm of the basal bulbs and terminal clubs of the tentacles is reddish-brown and 

 of the manubrium yellowish-brown. The ocelli are black. 



This medusa has been taken at infrequent intervals off the southern coasts of England and 

 Ireland. The best modern descriptions are given by Browne, 1898, and by Hartlaub, 1907. 



It is distinguished by the 4 small swellings on the 4 radial-canals. According to Browne 

 these are probably glandular, but Hartlaub regards them as gonads which develop later than 

 the gonads upon the manubrium. Hartlaub, apparently, has not sectioned the medusa, while 

 Browne bases his conclusions upon a study of sections. 



Slabberia strangulata Haeckel. 

 Plate 7, figs. I, 2, and 3. 



Dipurtna strangulata, McCRADY, 1857, Gymn. Charleston Harbor, p. 33, plate 9, figs. I, 2. 



Dipurena cervicata, McCRADY, 1857, Gymn. Charleston Harbor, p. 34. 



Dipurena conica, A. AGASSIZ in L. AGASSIZ'S, 1862, Cont. Nat. Hist. U. S., vol. 4, p. 341. 



Dipurcna cervicata, AGASSIZ, L., 1862, Cont. Nat. Hist. U. S., vol. 4, p. 341. 



Difurena strangulata, AGASSIZ, L., 1862, Cont. Nat. Hist. U. S., vol. 4, p. 341. 



Difurena conica, AGASSIZ, A., 1865, North Amer. Acal., p. 181, figs. 301, 305. 



Dipurena strangulata= Slabberia strangulata, HAECKEL, 1879, Syst. der Medusen, p. 23. 



Dipurena conica, HAECKEL, 1879, Syst. der Medusen, p. 24. 



Dipurena strangulata, FEWKES, 1881, Bull. Mus. Comp. Zool., vol. 8, p. 155, plate 4, fig. 5. BROOKS, 1882, Studies Johns 



Hopkins Univ. Biol. Lab., vol. 2, p. 136. 



Dipurena conica, VERRILL, 1873, Report Commiss. Fish and Fisheries for 1871-72, p. 735. 

 Dipurella clavata (immature), HARGITT, 1904, Bulletin of the Bureau of Fisheries, vol. 24, p. 31, plate I, fig. 3. 

 Dipurena conica, NUTTING, 1901, Bull. U. S. Fish Commission for 1899, vol. 19, p. 373. HARGITT, 1901, American Naturalist, 



vol. 35, p. 578, fig. 34. 

 Purena strangulata, HARTLAUB, 1907, Nordisches Plankton, Nr. 12, p. 55, fign. 51-53. 



In 1857 McCrady described those which he believed to be two distinct species of Difurena, 

 D. strangulata and D. cervicata, from Charleston Harbor, South Carolina. In 1862-65, 

 A. Agassiz described that which he believed to be another species, from Buzzards' Bay, under 

 the name of D. conica. A careful study of Dipurena in Charleston Harbor, in September, 1897, 

 when the medusae were exceedingly abundant, has convinced me that all of these forms are one 

 and the same species. McCrady found only two individuals of D. strangulata and one of 

 D. cervicata, and thus A. Agassiz was misled into the assumption that the northern form was a 

 distinct species. The shape of the bell is, however, very inconstant, and the length of the 

 manubrium in the Charleston medusae is subject to a wide range of variability. 



Adult medusa (plate 7, fig. i). The bell is quite variable in shape, for in some individ- 

 uals it is hemispherical, while in others it is ellipsoidal and higher than a hemisphere. All 

 gradations between these two extremes are observed. In a large individual in which the bell 

 was hemispherical it was 4 mm. in diameter; while another having an ellipsoidal bell was 4 mm. 

 in height and 3 mm. in width. There are 4 stiff tentacles, one at the base of each radial- 

 canal. Each tentacle terminates in a single, knob-like swelling which is covered with nema- 

 tocysts. The entodermal core of this swelling is hollow, and its lumen is placed in communi- 

 cation with the general gastrovascular system of the medusa by means of a narrow thread-like 

 canal which extends through the entire length of the tentacle. The basal bulb of each tentacle 

 is large and there is a single, ectodermal ocellus mounted upon a short pedicel, upon the outer 

 side of the bulb. The tentacles are all of equal length, and each one is about three-fourths as 

 long as the bell-diameter. The velum is wide. There are 4 straight, simple radial-canals 

 and a narrow, circular tube. The gastric cavity projects upward a short distance into the 

 gelatinous substance of the bell at the point of intersection of the 4 radial-canals. The manu- 

 brium is always long and increases in length with advancing age. In mature medusae it projects 

 far beyond the velar opening and varies in length from 5 to 10 mm. It is tubular and highly 

 contractile, and the mouth is a simple, round opening. Four distinct regions may be distin- 

 guished upon the manubrium of the mature medusa. First, a long, narrow, tubular region, 

 extending from the inner apex of the bell-cavity to about the level of the velar opening, then a 

 short, fusiform, swollen region, then a short, narrow, tubular region similar in size to the 



