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Show 166 PROF. F. J. BELL ON BIPALIUM KEWENSE. [Mar. 16, 3. Note on Bipalium kewense, and the Generic Characters of Land-Planarians. By Professor F. J E F F R E Y B E L L, M.A., Sec. R.M.S. [Received March 16, 1886.] (Plate XVIII.) In the descriptions given by writers on Land-Planarians especial attention is always directed to the form of the head or, as more than one author has called it, the tail. This, no doubt, is partly due to the fact that in a number of the species the head is often seen to have a remarkable hammer-shaped or cheese-knife form, which has three times led to the institution of a genus for the reception of such species. In other cases, where the worm has been assigned to other genera, the head is described as obtusely rounded, or as not sharply distinguished from the body. Having lately received from Mr. Osbert Salvin, F.R.S., a specimen of a Land-Planarian (apparently Bipalium kewense, Moseley), found by him among broken flower-pots in his garden in Sussex, of the origin of which nothing definite is known, I have been euabled to watch the creature exhibiting its activity. I had not long been studying it when I noted that the head varied considerably and almost constantly in form, so that I thought it well to at once enlist the skilful pencil of Mr. C. Berjeau to represent its various appearances. Figure A represents the worm, not indeed at its greatest length, but in a position which it is apt to assume when in full activity ; the head is carried a little higher than the rest of the body, its edges are sharp, its contour convex, and it is well marked off from the rest of the body. Figure B, on the other hand, shows the animal in a state of torpid quiescence; the head is now contracted, obtusely pointed, only separated by a shallow depression on either side from the surrounding region of the body. Fig. C shows an intermediate condition between A and B. Figs. D - G show various stages in the form of the head1-hammer-shaped, knob-like, tongue-shaped, or altogether irregular. The body may be not more than 2 inches long, when the creature looks like a leech or a slug, or it may extend itself to 6 inches and even more, when it has rather the appearance of a thread-worm. In fact, as one looks at it extended on a white dish, it calls to mind the Amoeba more than any other animal known to the zoologist. I insist on the variations in the form of the body, and especially of the head, because all writers (even those who, like M . Humbert, Prof. Moseley, or, the latest of all, Dr, J. C. C. Loman, have had the opportunity of examining these forms alive or under natural conditions) direct, in their descriptions, especial attention to the form of the head ; indeed, land-planarians with cheese-cutter or hammer-shaped heads (cf. figs. A and D) have been by all naturalists ' All the figures are of the natural size. |