A PIECE OF HORNWRACK, ETC. 7 



It is however of the first species, F. foliacea^ or " the Broad 

 Leaved Hornwrack," that I propose to write at present. Taking 

 it into the hand, it appears like brownish sandpaper, but placed 

 under the microscope the roughness of its surface is seen to be 

 caused by innumerable cells ranged semi-alternately, and each 

 shaped, as Mr. Gosse not unaptly suggests, like a child's cradle, 

 narrow and straight for the lower half, and bulging out into a 

 semicircle in the upper half, with a couple of blunt spines on each 

 side of the upper margin, and often a single one in the centre. A 

 reference to Plate I., Fig. 2, will show the appearance of the cells 

 under the microscope. 



The Rev. P. H. Gosse in " Tenby " ^ has published a calcula- 

 tion showing the number of cells in a square inch of the Fhistra. 

 He reckoned these to be as many as 6,720, and as there are, in 

 many specimens, at least 5 square inches on each side, it follows 

 that the cells number not less than 67,200. The inhabitants of 

 these cells exhibit the characteristic polyzoan structure. From the 

 orifice of each cell when aHve a bell of tentacles may be seen 

 protruding, in the centre of which is the mouth leading into an 

 oesophagus, and thence to a stomach and intestine. The latter 

 opens outside the bell. Attached to the oesophagus on one 

 side is a small nervous ganglion. The polypide is connected 

 with the base and sides of the cell by a structure known as the 

 funiculus^ which passes through the base of the cell and serves not 

 only as the usual source of origin of the reproductive organs, but 

 also as the connecting link between the various members of the 

 polyzoan colony. From the sides of the cell (which is called the 

 zooeciuni) to the stomach and tentacles extend a series of muscles 

 serving to expand and retract the tentacles and their sheath, and 

 to unfold and fold the body of the polypide The growth of a 

 colony takes place by gemmation, but new colonies are formed by 

 sexual reproduction. 



. The Polyzoa occupy a very undecided position in the scale 

 of classification. They are considered by some as belonging 

 to the Vermes, but by most English naturalists they are included 

 among the Molluscoida, a sub-division of the Mollusca. The 



* "Tenby, a Sea-side Holiday," by Rev. P. H. Gosse, p. 196, where a 

 most poetical but interesting and accurate description of this species is given. 



