33 SAGAKTIAD.E. 



Of foreign species the beautiful S. decor ata (Dan a), found 

 in the Lagoon of Honden Island, is closely allied to our 

 bellis. 



S. Fuegensis (Dana), from Terra del Fuego, a very fine 

 species with rich yellow column and disk, and grass-green 

 tentacles, has much in common with the subject of this 

 article, but it has far more prominently the characters, that 

 the tentacles are short, and spring isolatedly from the disk. 



S. impatiens (Dana) has the habit of elongating the 

 column pillar-wise, and of variously constriuging and writh- 

 ing the body ; thus appearing to be intermediate between 

 bellis and viduata. 



It seems to be through bellis and Fuegensis, that the 

 genus Sagartia leads off to the curious Discosoma 

 nummiforme of the Red Sea, in which the column 

 has no appreciable height, the animal being a very 

 thin, flat, circular plate, with the tentacles reduced to 

 minute warts, arranged in groups which form radiating 

 bands. 



Of native species S. parasitica and B. clavata present, in 

 the expanded character of their disks, marked relations 

 with lellis. But a still closer affinity exists between bellis 

 and Aiptasia amaclia, in the characters both of the disk and 

 of the column, as I shall notice more particularly when I 

 come to describe the latter. 



It ought never to be forgotten that the order of sequence 

 which we are compelled to adopt in treating of creatures 

 in a book — that of placing each species between two others 

 — can by no means express all their relations. Every 

 species stands in the midst of many others, some closer to 

 it, some more remote, to which it is linked more or less 

 obviously. " Ten or twenty links would often be insuffi- 

 cient to express these numerous relations."* To obviate 



* Cuvier. 



