156 THREE CRUISES OF THE "BLAKE." 



this species are alternately large and small, with very long digi- 

 tiform tentacles. The figure (Fig. 482) represents them as they 

 are frequently disposed, the larger polyps alone being visible, 

 while the smaller ones can only be seen in the profile view. At 

 other times the tentacles are very much shortened and stiffened, 

 and stand out from the axis. The singular mode of growth of 

 Antipathes columnaris (Fig. 483) deserves a few words of 

 description. The central hollow column is occupied by an an- 

 nelid which appears to compel the corallum to form an abnormal 

 growth of that shape. Every one of the specimens dredged 

 was similarly affected, and the annelid was still in place in most 

 cases. A similar action of parasitic annelids has been noticed in 

 some true corals, such as Lophohelia, Stylaster, Allopora, and 

 others. 



