SERTULARIA. 163 



Naturee, or in other systems ; or whether authors have in fact identifie d 

 any one of such peculiar formation as to be exclusively thus denominated. 



The figure given by Ellis, Plate X. a, N. 15, as the Sertularia hale- 

 cina, is certainly from an indiiferent drawing of what is named Thoa 

 Beanii in Dr Johnston's useful work, Plate VI. 



Thus the description and concomitant figure by Ellis do not distin- 

 guish any species recognized as the Sertularia halecina exclusively. 



But there are several reasons for assuming that this species is seen 

 under considerable modification, which has induced naturalists to esta- 

 blish as others, what may be perhaps only varieties. Some of these are 

 certainly cognates — children of the same family. 



Whatever may be the real critical distinctions among them, many 

 interesting facts are disclosed by perfect specimens falling under observa- 

 tion. Therefore, while abstaining from all further controversy on the 

 point, which can be of little importance to most readers, I shall speak only 

 of a few individual corallines by this general name, which have occurred 

 from time to time in the course of my investigations into the nature of 

 zoophytes. 



1. Among several specimens obtained on the last of December, one 

 arose four inches high by a brownish stem, composed of aggregated tubuli, 

 with large boughs diverging to right and left, each of which might be cir- 

 cumscribed by an isosceles triangle. This peculiar formation distinguished 

 the other specimens, as it does also those consisting merely of a stem with 

 diverging boughs, void of farther subordinate parts. All the boughs stood 

 at an acute angle with the stem ; likewise the branches with the boughs ; 

 and still more conspicuously the numerous twigs on each side of the 

 branches, — the whole of these parts being in alternate arrangement. The 

 prevalent colour of this specimen was greenish. Some very slender and 

 diminutive, apparently mature white parts, are frequently seen on speci- 

 mens, which seem neither spurious nor parasites. Though the stem be 

 compound, the more remote organization, in as far as sensible, resolves into 

 simple tubes. — Plate XXVII. 



Hydrse of the wonted form, with 18, 20, or 22 muricate tentacula 



