Royal Physical Society. 263 



the usual notion that the flints occasionally found on the shores of the 

 Forth were the remains of ship-ballast, and gave it as his opinion that 

 they were the wreck of cretaceous strata, which formerly existed in the 

 neighbouring sea, and were a prolongation of the Denmark beds. 



III. Observations on British Zoophytes. On Tubularia indivisa. By 

 Thomas Strethill Wright, M.D., Fellow of the Royal College of 

 Physicians, Edinburgh. (See Plate XV.) (For description of Plate 

 see p. 253.) 



The object of this notice is to elucidate some points in the 

 anatomy and physiology of Tubularia indivisa which have 

 escaped detection by, or presented difficulties to, the nume- 

 rous authors who have written on this zoophyte. 



This species of Tubularia, as many members of the Society 

 are well aware, is common in the Frith of Forth, where it is 

 dredged up from the oyster-beds in considerable quantities. 

 It resembles, as Ellis has remarked, an oat-plant with the 

 straws topped or truncated at from two to eighteen inches 

 from the root, each stem bearing at its summit a single polyp 

 of a white, pink, or rich crimson colour, and furnished with a 

 double row of tentacles. In describing the anatomy of this 

 zoophyte, I shall take the different parts in the order I have 

 observed in my communication on the anatomy of Hydractinia, 

 viz., — 1st, the corallum ; 2d, the polypary ; and, 3d, the polyp. 

 The corallum, or polypidom, is a simple yellowish chitinous 

 tube, straight or slightly flexuous. It is often divided at the 

 base, so as to form sinuous quasi roots, which creep over shells 

 and stones, and occasionally the coralla of other zoophytes, re- 

 sembling, as Ellis quaintly observes, " the guts of small ani- 

 mals." Many tubes are often found twisted together by the 

 roots. The tube of the corallum increases in diameter from 

 its attachment upwards, and is marked at irregular distances 

 by wrinkles or annulations. The chitinous substance is brit- 

 tle, cutting cleanly between the scissors, without splitting, but 

 its illuminating action on the dark field of the polariscope 

 indicates that it is composed of fibres running in a longitudi- 

 nal direction. 



The polypary, or that part of the animal which is inclosed 

 within the corallum, presents a structure of great interest. 



