SERTULARIA. 151 



arrangement. This peculiar arrangement is the true formation of the 

 adult, though the cells sometimes appear nearly in pairs. About 45 cells 

 are on each side of the longest branch, and one on each side of the short- 

 est. The branches issue from the convexities of the stem. An elegant 

 recur vature, as of an ostrich feather, distinguishes this product, which is to 

 be ranked among the larger flexible zoophytes. As all the parts diverge 

 in the same plane, a specimen such as described might be sunk in the 

 thickness of ordinary pasteboard. — Plate XXIII. 



The cells, which are ventricose, or swelling in the middle, are inha- 

 bited by a grey or white hydra, protruding a long cylindrical neck and 

 head, with about 24 muricate tentacula. These tentacula appearing to 

 the eye a little enlarged, like so many rows of beads, environ a hemi- 

 spherical central pouch. The hydra is quick and active, but not readily 

 obtained alive. At least the proportion has been small amidst a number 

 of specimens. 



The species occurs in considerable profusion in the sea, at the depth 

 of several fathoms, commonly rooted on old deserted shells. As if dwell- 

 ing in society, many specimens are often found in close approximation. 

 Those of larger dimensions are profusely invested by a minute, testaceous 

 animal, the Spirorbis, or by another zoophyte, the Cellaria, or Crista 

 eburnea. 



Recent living specimens are universally of a yellowish colour — honey- 

 yellow ; others, like many marine productions, have acquired an unnatural 

 reddish hue.* 



Naturalists understand the figure of the ovarian vesicle as a specific 

 character of the Sertulariae ; but this opinion must be received under mo- 

 difications sometimes perplexing, and yet insufficiently explained. 



Vesicles are either simple or compound, that is, consisting of a single 

 pod, with its contents, affixed immediately to the specimen, or of one 

 more complex, being a pod sustained by an intermediate organization. 



* The nomenclature of colours employed here is from a work on that subject by the 

 late Mr Peter Syme, an accomplished artist, founded on one by Werner. Many drawings 

 were executed for me by that artist. 



