29 
NOTES on the Structure of ALCYONIDIUM GELA- 
TINOSUM. 
By JosEpH Lomas, Assoc. N.S.S., 
SPECIAL LECTURER ON GEOLOGY IN UNIVERSITY COLLEGE, LIVERPOOL. 
With Plate ITI. 
[ Read 12th February, 1887.] 
THis species of Polyzoon, so common in the rock pools 
round our shores, has attracted much attention from 
naturalists. 
Sowerby, in his “‘ English Botany,” and Lamarck and De 
Candolle, in their ‘‘Flore Francaise,” i1., p. 6, believing it 
to be a plant, describe 1t under the name of Ulva diaphana. 
John Ellis, F.R.S., in his ‘‘ Kssay towards a Natural 
History of the Corallines,” (1755), plate xxxii., figs. D.d., 
p. 87, calls it Alcyonum seu Fucus nodosus et spongiosus. 
He made transverse sections, and after remarking that the 
species needs more critical enquiry, suggests that 1t may 
be the spawn of some shell fish. 
In the works of Linneus, Pallas, Ellis and Solander, 
Lamouroux, &c. it goes by the name of Alcyoniwm gela- 
tinosum ; and was first placed in the Polyzoa by Lamouroux. 
Van Beneden calls it Halodactylus diaphanus, in his 
|Reeherches- sur les Bryozoaires,” p. 59; and under 
‘the same name, Dr. Farre (Phil. Trans., 1837) gives a 
most valuable and interesting account of the species. 
The name has now been changed to Alcyonidium gelatino- 
sum, and is so described in all recent works on the subject. 
The colonies are found adhering to rocks, stones and 
dead shells, and range bathymetrically from tide mark to 
40 or 50 fathoms. ‘The young colony is of an elongated 
