12 Lightbown, Filaments in the Siphonozooids of Pennatulacea 



average 0.3 m.m. in diameter, with a stomodaeum measuring 0.2 

 m.m. in dorsiventral. diameter and every coelenteron appears to be 

 almost filled with the large convoluted filaments, 0.096 m.m. in 

 greatest width ; so that at any level of a series of transverse sec- 

 tions a single filament may be cut through transversely two or three 

 times, or may appear cut longitudinally for a length of .2 to .3 m.m. 



In describing a specimen taken by the "Discovery" Hickson 

 (1907 p. 13) refers to the small siphonozooids from the upper part 

 of the bulb, which he examined in transverse section, and says of 

 these : "The specimen is not sufficiently well preserved to enable me 

 to state definitely that the dorsal mesenteric filaments are present, 

 but certain groups of darkly stained cells situated below the stom- 

 odaeum probably represent these structures. " I have examined the 

 preparations mentioned and though the material is not sufficiently 

 well preserved to show any minute structure, the position and 

 stained condition of these bodies justifies the supposition that they 

 represent filaments. 



U. gracilis, Marshall. = U. Lindahli, Kolliker. 



Mesenteric filaments in the siphonozooids are described by Mar- 

 shall for a specimen trawled by the "Triton" (1883 p. 146) but the 

 statement and accompanying diagram (Plate XXV. fig. 33) refer 

 to the large tentacular siphonozooids towards the top of the rachis, 

 and while the author mentions that the zooids decrease in size to- 

 wards the base of the rachis, he does not state if filaments are 

 present in all. Jungersen identifies the U. Lindahlii of Kolliker 

 with the above species and confirms the observation of filaments 

 (1904 p. 77). 



U. Jordani, Nutting. 



In this species also the filaments are well developed, being of 

 considerable length, and coiled, though not to the same extent as 

 those in U. Carpenteri. 



OSTEOCELLA SEPTENTRIONALIS, Gray. 



Siphonozooids in this large fleshy sea-pen occur scattered on the 

 dorsal track of the rachis and between the leaves, and in all 

 mesenteric filaments are well developed. 



Pavonaria finmarchica, Sars. 



Pavonaria (Halipt. ) Christii, Koren and Danielssen. 



Of the first of these species Kolliker (loc. cit. p. 242) referring 

 to the siphonozooids, says "die ich als die zwei langen Mesenterial- 

 filamente deute, die bei den Zooiden so vieler Pennatuliden sich 

 finden : " of the second species which was described under the 

 generic name Halipteris a similar observation is made (p. 248). 



