310 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.37. 



OBELIA GENICULATA (Linnaeus). 



Sertularia geniculata Linn-EUS, 1776, No. 1312. 

 Ohelia geniculata Allman, '64, p. 372. 



The collection contains many specimens of Ohelia from St. Pierre, 

 off Newfoundland, October, and from Fogo Island, Ne\\'foundland, 

 July 28. 



They are all far advanced in development. In the position of the 

 gonads they resemble the figures of 0. geniculata given by Bohm 

 ('78, pi. 3, figs. 1-34). This species has already been recorded by 

 Nutting ('99) from Woods Hole, Massachusetts, and on the coast of 

 Europe is widely distributed. The identification can, however, be 

 only provisional, inasmuch as a knowledge of the hydroid stages is 

 essential for final determination. 



TRACHOMEDUS.^. 



The collection contains two species of Trachomedusae, one belong- 

 ing to the remarkable and still obscure genus Ptychogastria, the other 

 to Aglantha. 



PTYCHOGASTRIA POLARIS Allman. 

 Ptychogastria polaris Allman, '78, p. 290, figs. 1-3. 



Four specimens, 13 to 21 mm. in diameter, from between Cape 

 Mugford and Hebron, Labrador, August 23, in the dredge, from 60 

 fathoms. Unfortunately, all of the specimens are in such poor con- 

 dition that I can do little more than corroborate the excellent account 

 of this species which we owe to Browne (:03), who has shown that the 

 description by Haeckel ('79, '81, PectylUs arctica) is incorrect in several 

 particulars. Its synonymy and history have recently been discussed 

 by Maas (:06, p. 582). The most remarkable feature of Ptycho- 

 gastria is the fact (demonstrated by Browne) that although the pres- 

 ence of free club-like otocysts undoubtedly places it among the 

 Trachomedusse, the gonads are situated not on the radial canals, but 

 on folds of the walls of the manubrium. Maas, it is true, has doubted 

 whether the sexual organs are truly stomachic. But my examination 

 of the present specimens, in which the manubria were fairly well 

 preserved, has convinced me that Browne is correct in maintaining 

 that the gonads belong exclusively to the walls of the stomach and 

 that no sexual products are developed on the radial canals. 



The question whether or not there are sixteen distinct gonads, as 

 Browne maintains, or whether Maas (:06, p. 483) is correct in saying 

 that there are only eight, but that " Jede der 8 Gonaden erscheint 

 iibrigens durch die Ansatzlinie der Mesenteriums scharf zweigeteilt 

 so dass man eigentlich von 16 Gonadenlamellen sprechen konnte" 



