300 ZOANTHID.E. 



In this condition, the zoophyte was mistaken by Dr. G. 

 Johnston for a Sponge, and he has accordingly figured and 

 described it in his " British Sponges," under the name of 

 Dysidea papillosa. I do not see in what single particular such 

 specimens differ from the genus Palythoa of Lamouroux, 

 as this is characterized by M. Milne Edwards : — " Poly- 

 piero'ides cylindriques, naissant sur une expansion hasilaire 

 rnembraniforme, libres lateralement, ou sondes entre eux, et 

 formant des masses encroutantes ; " * and thus we find the 

 same species in some circumstances a Zoanthus, in others a 

 Palythoa. Nay, more, as if to increase the confusion, Dr. 

 J. E. Gray has actually made a new genus for the inter- 

 mediate free condition, which he calls " Sidista."^ 



The only way in which I can account for the free condi- 

 tion is by supposing that the germ was, in those cases, 

 deposited on a fragment of shell or stone so minute as to 

 be completely overspread and enveloped by the increasing 

 base.* The unvarying disappearance of the shell in the 

 diffuse variety is more remarkable, and seems to imply a 

 corrosive or absorbent power in the base. 



That the Shetland and Northumberland specimens are 

 identical with ours in Torbay seems pretty certain ; for Mr. 

 Alder, who has had opportunities of seeing both in the 

 living state (some from the north having been sent him alive 

 by Mr. Barlee, and some from the south by myself), can see 

 no specific diversity between them. But that they are the 

 same species as the Zoanthus Couchii of the Cornish coast, 

 I assume rather than prove. It is unlikely that there should 



* Hist, des Coralliaires, i. 301. t Annals Nat. Hist. Dec. 1858. 



\ Mr. Alder remarks on these varying conditions as follows : — " I have 

 come to the conclusion that when the zoophyte has free space on a stone 

 it runs over it as Zoanthus ; but when the base is confined to a shell, it 

 spreads into an uniform crust, as Palythoa. The loose bi-anched speci- 

 mens, I conclude, having affixed themselves to some minute object not 

 affording a proper base of attachment, take a tubular form until they 

 terminate in polypes." — (In lift. J 



