60 Proceedings of the Royal Physical Society. 



fathoms water, 30 miles from Holy Island. Mr Alder's de- 

 scription of it is as follows : — " Tubularia 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 Tubularia 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 

 ccenosarc 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, (b), 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. 



