300 
ZOANTHID^. 
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 hasilmre 
memhraniforme, lihres lateralement, ov. soudes entre eux, et 
formant des masses encroutantes / ” * and thus we find the 
same species in some cireumstances 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 “ Sid{sia.”\ 
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.j 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 speeies as the Zoanthus Conchii of the Cornish coast, 
1 assume rather than prove. It is unlikely that there should 
* Hist, dea CoralHaires, i. 301. f Annals Nat. Hist. Dec. 1858. 
J 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 branched speci- 
mens, I conclude, having affixed themselves to some minute object not 
affording a proper base of attachment, take a tubular form until they 
tei'minate in polypes .” — ( In litt.) 
