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London: ROBERT HARDWICKE, 192, PICCADILLY, W. SECOND-HAND MICROSCOPES, By Smith and Beck, Ross, Pillischer, and others. ASTRONOMICAL, TOURISTS', SLING, AND SEASIDE TELESCOPES. Magic and Dissolving-view Lanterns and Slides. RACE, FIELD, AND OPERA GLASSES. SURGICAL, MATHEMATICAL, AND SURVEYING INSTRUMENTS, AT WILLIAM LAWLEY'S, 78, Farringdon Street, City. Enlarged and Revised Catalogues of nearly 100 Pages for Three Stamps each. Enlarged Illustrated Surgical Catalogue, Six Stamps. MICROSCOPE MAKER AND MANUFACTURING OPTICIAN. (Many years with the late A. Ross.) NEW IMMERSIONIN. OBJECTIVE, giving brilliant definition under deep eyepiece power, complete, with Adjustment in Box, £5; dry front, if required, extra £2. SWIFT'S IMPROVED TEN-GUINEA BINOCULAR MICROSCOPE.-This instrument for efficiency of action, durability, and cheapness, is unapproached. An Illustrated paper forwarded for Stamp. J. S. has just completed a new and extensive Illustrated Catalogue, of 32 pages, of Microscopes and accessories, containing a new and revised list of Objectives. Sent free for one Stamp. 43, University St., Tottenham Court Road, London, W.C. CONTENTS OF No. XXXIII. I. ON A NEW ROTIFER. By C. T. Hudson, LL.D. .. III. ON SPECTRA FORMED BY THE PASSAGE OF POLARIZED LIGHT THROUGH DOUBLE-REFRACTING CRYSTALS SEEN WITH THE MICROSCOPE. By Francis Deas, M.A., LL.B., F.R.S.E. .. IV. REMARKS ON SOME PARASITES FOUND ON THE HEAD OF A BAT. V. NOTE ON THE RESOLUTION OF AMPHIPLEURA PELLUCIDA BY A VI. MICRO-RULING ON GLASS AND STEEL. By John F. Stanistreet, F.R.A.S. With Illustrative Remarks by Henry J. Slack, VII. THE FUngoid Origin of Disease, and Spontaneous Generation. The MONTHLY MICROSCOPICAL JOURNAL is furnished free to Members of the Royal Microscopical Society. Non-Members can get it from any bookseller, Contributors must write their Names and Addresses on the first page of MS. All Communications to be addressed to the Editor, 192, Piccadilly. a THE MONTHLY MICROSCOPICAL JOURNAL. [Sept. 1, 1871. ROYAL MICROSCOPICAL SOCIETY. (Founded in 1839. Incorporated by Royal Charter 1866.) HE Monthly Meetings of the Royal Microscopical Society will commence THE on Wednesday, the 4th of October, and be continued on the First Wednesday of each month at King's College, Strand, at 8 o'clock P.M. Visitors are admitted by introduction of Fellows. The Library and Reading-room is open for the use of Fellows on Mondays, Tuesdays, Thursdays, and Fridays, from 11 A.M. to 4 P.M.; and on Wednesdays, from 7 to 10 P.M. Every candidate for admission as a Fellow must be proposed by three or more Fellows, one of whom must have personal knowledge of him. The admission fee is 27. 28., and the annual subscription 21. 28., payable in advance. The annual subscription may at any time be compounded for by a payment of 211. Fellows who may be elected in the months of October, November, or December shall not be called upon for a second subscription during the ensuing year. The Fellows are entitled to receive the publications of the Society. The Society's Proceedings and Transactions appear 'regularly in the Monthly Microscopical Journal.' Forms of proposal for Fellowship, and any further information may be obtained by application to Mr. WALTER W. REEVES, Assistant-Secretary and Librarian, King's College, London. THE MONTHLY MICROSCOPICAL JOURNAL. SEPTEMBER 1, 1871. I.-On a New Rotifer. By C. T. HUDSON, LL.D. PLATE XCIV. A ROTIFER hunter should never pass a pond without trying it, no matter how often he has been disappointed before. For example, here is a pond close to my house, which, so far as I can remember, has never yielded anything worth catching for many summers, and yet this July I have taken in it in one dip several specimens of Synchæta, Åsplanchna, Brachionus, and Anuraa, as well as of a new and very extraordinary rotifer. On hunting over the bottle with a hand lens before taking it home, I readily recognized the first four, while the latter I supposed to be some new and unusually large species of Polyarthra ; but on placing a specimen under the microscope I for a moment doubted whether it was a rotifer at all, and not a larva of some one of the Entomostraca. A brief examination showed the animal to be a true rotifer with a splendid trochal disk and ciliated chin, and with internal organs much like those of Triarthra, but with an external form of a most unusual character; for it possesses six well-defined limbs containing powerful muscles, and terminated not by cilia but by fan-shaped plumes of fringed hairs, and is in these respects so utterly unlike any other rotifer, that, though it has many points of resemblance to the Hydatinæa, I am quite puzzled where to place it. I propose to call it Pedalion mira, from the oar-shaped limb with which it steers its way like an ancient trireme; occasionally however improving on its antique type by striking a succession of vigorous slaps with all its limbs in concert, and darting through the water with such speed as to clear quite sixty times its own length. EXPLANATION OF PLATE XCIV. FIG. 1.-Front view, showing the dorsal antenna, eyes, double row of cilia round the trochal disk, and the mouth lying between them and above the ciliated chin. 4.-Pseudopodium; ventral surface. All the figures are on the same scale, and represent a magnification of about 300 linear. VOL. VI. K in a second, that is to say, at a rate which in a man would be upwards of 200 miles an hour. Every new rotifer is a new difficulty. Hydatina is troublesome enough, for it is never still, and will not bear compression. Synchata has in addition the charming habit of turning over head and heels. Triarthra and its small cousin Polyarthra by help of their spines and plumes add skipping to their other accomplishments, and were, till I found Pedalion, the most vexatious of all the rotifers. But while they are chary of using their full powers-reserving them for great occasions, such as when they fall foul of each other or run against the sides of their prison-Pedalion skips habitually without the slightest provocation, and at tolerably regular intervals, so as to drive an observer into a fit of nervous irritation. Now it is hopeless to attempt to make out its shape or internal structure unless the creature can be kept tolerably still, and yet I found it impossible to hit upon any way of ensuring this at my own pleasure. If I secured Pedalion between the two plates of the compressorium, it was only to see its limbs reversed and thrown into unnatural attitudes, hiding often the very things I wanted to look at. If I placed it in a very tiny drop of water and gave it just room to swim in, before many minutes had elapsed it either jerked itself half out of the drop and lay sprawling, helpless, and disfigured; or with its back adhering to the concave boundary of the water it kept "squirming around" (as a young American lady described it to me) like a horse in a circus. It was clear that, unless the rotifer would of its own accord sit for its portrait, there was no Plate to be had for the 'Microscopical Journal,' so I abandoned the heroic methods and tried coaxing and patience. I first placed one or two scraps of conferva on the under-glass of the compressorium so as to cross each other, and then I went to my tank in which the rotifers were, and, watching till the currents that are always rising and falling in it, had swept into one corner a tolerably dense crowd of them, I drew up a score or two with a pipette, and dropped them with as little water as possible on the interlacing weed. On placing the cover over them, and gently compressing the weed, I had of course many rotifers entrapped in small live cages deep enough for them to swim in pretty freely without getting far out of range. It was a pretty sight to see them darting about, diving, skipping, and rolling in every direction; but I began to fear that my scheme would fail, for I seemed to have made them more restless than ever. After a while, however, they seemed to get tired, or to be reconciled to their prison, and then one or two settled down to exploring the confervæ, sailing along with their mouths and |