Mr. E. W. II. Holdsworth on Zoanthus Couchii. 155 



On the 9th of November last, Dr. Gray brought before this 

 Society a notice of a curious form of Zoanthus sent to him by Mr. 

 George Barlee from the Shetland seas, and for the reception of which 

 he proposed the new genus Sidisia. He has kindly allowed me to 

 describe this polype ; and it is therefore with some regret that, after 

 a careful examination of it, I must question its generic or even spe- 

 cific distinction from Zoanthus Couchii, the subject of the previous 

 part of this paper. The great peculiarity of these polypes consists in 

 their being entirely free, no parts of the specimens at the British 

 Museum showing any superficial trace of attachment. Another 

 remarkable character is their irregular mode of budding, and may be 

 briefly described as one polype growing out from another without the 

 intervention of the usual connecting bands ; this budding takes place 

 from the base of the parent polype in an opposite direction, or at 

 various angles with the original line of growth, the branches again 

 sometimes throwing out buds from near their own bases. Mr. Barlee 

 states that some of the specimens were attached, but most of them 

 came up in the dredge free, and that they abounded on muddy ground. 

 This situation is I think very significant, and sufficient to explain the 

 peculiarities of the animal. As I have before mentioned, it is the 

 habit of Zoanthus to be attached to some stone or shell, and the 

 first sign of its increase is in the expansion of the basal membrane 

 either on one or all sides of the polype ; from this expansion the 

 young bud forth at various distances from the parent, and they in 

 time develope similar offshoots. Such is the case when the ova fall 

 on places suited to their natural growth ; but if by chance they are 

 deposited on a muddy bottom, or where the stones are only large 

 enough to afford attachment to a single polype, I think an irregular 

 mode of growth may be reasonably anticipated, and a variation ex- 

 pected in the character which, above all others, is likely to be affected 

 by the change of circumstances. By the motion of the sea, the 

 position of these free polypes must be continually shifting, conse- 

 quently no part of their surface can be permanently uppermost ; and 

 under these circumstances, with a natural tendency to grow upwards, 

 regularity of budding would seem to be impossible. As might be 

 expected, scarcely two of the specimens I have seen are precisely 

 alike, which adds to the probability of the suggested explanation of 

 their irregular growth. The fact of the characters of the disk, and 

 the number of the tentacula and marginal divisions being identical 

 with those of the animals first described, is a strong argument also 

 in favour of their all being only different forms of the same species. 



Additional Observations, communicated March 8, 1859. 



Some fine groups of Zoanthus Couchii from Torbay having lately 

 come under my notice, I have been enabled to obtain a better know- 

 ledge of the species than I possessed when I recently laid before the 

 Society a description of its characters. I therefore venture to add 

 a few remarks on certain points, which before were considered as re- 

 lating to particular specimens, rather than to the species generally. 



