HYDROIDA II 27 



Colonies form upright, irregularly pinnate, polysiphonie rhizocaulomes, sometimes with creeping 

 parts. Hydrothecae long, tubular, some quite free and short-stalked, others with the one side for part 

 of its extent fused with the stolons; more or less curved, exceptionally with the distal part almost 

 perpendicular to the proximal. Diaphragm lacking. Closing apparatus formed by two folding thin 

 distal portions of the hydrotheca, shutting in a roof over the indrawn polyp between two strong, tooth- 

 like, diametrically opposite parts of the distal portion of the hydrotheca. 



The gonothecse are situated on the branches or on the stalk. They present the appearance of 

 gigantic hydrothecae, with the same structure of the closing apparatus. The gonothecae are entirely 

 free, short-stalked, or to a greater or lesser extent attached to the tubes. 



55°42' W.; 



54V W.; 



5 6° 3 8' W.; 



54°i7' W.; 



55°05' W.; 



i 5 ° 5 2' W.; 



Greenland: Davis Strait (without further details) depth 80 fathoms 

 Umanak ( — — — ) 



Ritenbenk ( — — — ) on sEga crenulata 



Godhavn ( — — — ) 



Kara Sea, "Dijmphna" (Type specimen of Stegopoma caricum.) 



This remarkable species shows an astonishing power of altering its appearance. One variant 

 is described by Lev in sen (1893 p. 37) as a distinct species, Stegopoma caricinn, from the fact that it 

 has, at the points of the branches, only three hydrotheca-bearing stolons. This feature, however, as I 

 have previously pointed out (1912 p. n), cannot be maintained as a specific character, since it may 

 occur in certain branches, while others of the same colony have four or five such tubes near the 

 point; very rarely, again, we may find the number of hydrotheca-bearing tubes reduced to two. It 

 was also pointed out, on the same occasion, that the hydrothecae can vary, being at times entirely free, 

 at others fused with the tubes. Free hydrothecae on creeping stolons assume entirely the same appear- 

 ance as in Stegopoma fastigiatum (Alder). 



The gonothecae are mentioned several times in the literature, and have been described by 

 Bounevie (1899 p. 73) as follows: "Gonangia large, cylindrical with circular opening at the distal 

 end". Kramp, (1913 p. 16) on the other hand, describes them in the same manner as noted in the 

 diagnosis, and gives excellent drawings. In the very extensive material at my disposal from Trond- 

 hjem Fjord, where the species is extremely frequent, I have often had occasion to observe the gono- 

 thecae, which in all cases agreed with Kramp's description. It might be imagined that the gono- 

 thecse would exhibit sexual dimorphism; up to the present, however, I have not been able to find 

 anything in support of this idea, and it must thus be presumed that the earlier descriptions were 

 based upon inadequate observation of the gonothecae. 



4* 



