364 Mr. J. Hogg on Tentacular Classification o/*2Soophyte3. has hitherto been done towards explaining the causes of the phaenomenon. When the above observations were made I was not aware of any instance of a change in the direction of the spiral; but since then. Professor Morren of Liege has pointed out to me the occurrence of a double direction in the spire formed by the twisting of the tendrils of Bryonia dioica ; and I have subsequently observed in the tendrils of a species of Passiflora a twisting not only in two opposite directions, but in alternately different directions for five or six times to the end of the spire. XLII. — On the Tentacular Classification of Zooiphytes, By John Hogg, Esq., M.A., F.R.S., F.L.S., &c. In his able and beautiful work on the ^ British Zoophytes,* Dr. George Johnston has reviewed most of the classifications that have as yet been brought forward for those extremely in-teresting animals, which have been generally called Polypes {Polypi) by most French naturalists, as well as for their struc-tures or habitations, that have received, of late, the common appellation of Polyparies {Polyparia) from the same writers. In the first place I may remark that three methods of clas-sification present themselves to the investigator of this por-tion of natural history ; first, that which is derived from the Polyparies or dwellings of the animals ; — the second is taken from the natural organization and forms of the animals alone, that is to say, from the Polypes themselves ; and the third, that method which may be founded on a combination of cer-tain characters deduced both from the animals and likewise from their dwellings. Now, as an example of the first method, in my sketch of the ^ Natural History of the vicinity of Stockton-on-Tees,' which was written in the spring of 1825, but not published until the year 1827, I introduced an arrangement of many of our native Polyparies, grounded chiefly on the views of our own illustrious zoophytologist, the accurate Ellis ; and in order that it may be clearly understood, I trust I may be pardoned for here subjoining an outline or synopsis of it.
BioStor
