60 Proceedings of the Royal Physicat Society. 
fathoms water, 30 miles from Holy Island. Mr Alder's de- 
scription of it is as follows : — " Tuhularia implexa. — Tubes 
small, very slender, generally more or less contorted below, 
smooth, wrinkled or regularly annulated beneath a smooth 
transparent epidermis ; slightly and subunilaterally branched ; 
the branches going off nearly at right angles to the stem, and 
a little constricted at their base; gregarious, forming a densely- 
tangled mass of half to three-quarters of an inch in height. 
The polyp of this zoophyte had not been observed, for which 
reason Mr Alder considered that its claim to a place in the 
genus Tubularia could not be fixed very decidedly. Its most 
remarkable feature is the structure of the corallum or polypi- 
dom, which is divided into two coats, as in Plate III., fig. 6; a 
structure hitherto observed only in one other species, the Cam- 
panularia caliculata of Hincks. Mr Alder kindly sent me a 
specimen of his Tuhularia implexa^ which, after a careful ex- 
amination I concluded to be, not a Tubularia, but a Coryne ; and 
I wrote to Mr Alder to that effect. Fortunately, although the 
specimen was destitute of polyps, portions of the polypary or 
coenosarc still remained, and I found in its tissues two kinds of 
thread-cells, the one oval, and containing a barbed dart (fig. 7, a), 
the other cylindrical, with almost truncated extremities, in 
which the thread was not conspicuous. (6), The first of these 
resembled very closely the oval, barbed thread-cells of Coryne 
decipiens; while the second, although much larger, evidently 
corresponded to the long, slender thread -cells found on the body 
within the corallum, and especially in the tips of the growing 
shoots of the last named zoophyte. 
The internal layer of the corallum is brown and of horny 
texture ; the external coat colourless and membranous. The 
first is frequently annulated ; the second not so, but is occa- 
sionally gathered in longitudinal folds. I am disposed to 
think that this coat is the " colletoderm," or glutinous cover- 
ing of the corallum (in this species highly developed and in- 
durated), separated from the inner coat by the action of the 
spirit in which the specimen was immersed. In all the 
Corynes I have examined, this " colletoderm " forms a thick 
layer over the corallum, especially in the neighbourhood of 
the polyp. 
