SEETULAEIA. 143 



ducts. All have fallen ; for their use being temporary, their subsistence is 

 transient. Though the pith itself be the chief obstacle to detecting the 

 minute formation of the inorganic parts of the living specimen, nothing is 

 less permanent. It totally disappears. Portions of the skeleton alone 

 remain, after preceding deperdition of life and organization ; for I believe 

 it to be true, that no more than what are comparatively mere fragments 

 of the perfect subject continue entire. 



If we are to ascertain the nature of the Sertularise, we should behold 

 them complete, as in every stage, and under every aspect. Endeavouring 

 to show the peculiarities of healthy, vigorous, and symmetrical animals, 

 from the figure and arrangement of their mouldering bones, would never 

 be satisfactory. 



After some details on the appearance and properties of various zoo- 

 phytes, we shall resume a more explicit view of the most interesting points 

 distinguishing their history. 



§ 1. Sertulabia Polyzonias, The Hoop Sertularia, — Plate XXII. 

 — ^The embarrassment regarding identity, which is very frequent, may 

 be perhaps avoided, by selecting specimens with prominent features for 

 illustration and commentary. They are apt to be undervalued if com- 

 mon, as we forget that what is rarely seen by observers is uncommon in 

 respect to them ; and that what is very common to us may be elsewhere 

 scantily distributed. Subjects always at command are generally ne- 

 glected ; whereas they should be of all others the best understood. At- 

 tempting to inform our neighbours from a type of absolute novelty, which 

 few, if any, but ourselves have beheld, would be a futile endeavour. 



Probably this Sertularia is designated Polyzonias, from several belts 

 or rings obscurely encircling the ovarian vesicles. 



Specimens rise four inches high, by a stem which is slightly waved. 

 It is meagrely provided with boughs and branches diverging to right and 

 left, at irregular intervals, in the same plane, so that the whole specimen 

 might be sunk in the thickness of pasteboard. Cells are ranged alter- 

 nately on both sides of the stem and subordinate parts, always originating 



