while fully concurring with Dr. Higgins in his high estimation of Mr. Wales' objectives, I am of the opinion that he (Dr. Higgins) has either made an error in his measurement of amplification (210 diameters with the No. 1 or A eye-piece), or that theth objective is very much underrated in magnifying power. All of Mr. Wales'th objectives which I have seen have been as near or nearer 4ths than 4ths in magnifying power; and below I give a Table of amplification of suchth objectives as are at hand; also two ths for comparison:

The measurements were made with a first-class stand and eye-pieces of Zentmayer, the image of a stage micrometer being thrown down by a Spencer's camera lucida, and measured at just ten inches from the eye; cover adjustment for 125th cover glass. It seems to me that there should be some uniform standard adopted by the different makers of objectives, so that the 4th of one maker may not be as high as the 4th of another maker; or ath of one be as high as a 4th of another; or, still worse, a 3-inch objective of one maker of precisely the same power as a 2-inch of another maker, which was just the case with two objectives which I had about one year since. If the objectives did not differ any more than the first three in the above Table it would be an improvement. The amplification which Dr. Higgins gives to his ths is as high as the highest 4th in the above Table.-EDWIN BICKNELL, Salem.

CORRESPONDENCE.

MR. STODDER'S LETTER.

To the Editor of the Monthly Microscopical Journal.

DR. HENRY LAWSON,
BOSTON, May 30, 1870.
Dear Sir, I have but just seen the Monthly Journal for May,
my copies for April and May not having arrived yet.

Please publish the following errata in my letter in the May number:-Page 257, 13th line from bottom, 1868 instead of 1848; page 268, 14th line from top, Bicknell for Micknell; page 259, 5th line from top, 19th band instead of 17th.

Yours most respectfully,

CHARLES STODDER.

PROCEEDINGS OF SOCIETIES.*

ROYAL MICROSCOPICAL SOCIETY.

KING'S COLLEGE, June 8, 1870.

Rev. J. B. Reade, M.A., F.R.S., President, in the chair.

The minutes of the last meeting were read and confirmed.

A list of donations to the Society was read, which included Part 2, vol. clix. of the Philosophical Transactions' from the President. The usual vote of thanks was given to the respective donors.

Mr. Hogg stated that he had received a letter from Dr. Maddox, enclosing six photographs of L. curvicollis, most of which gave decided indications of beaded structure. As the letter contained points of interest it is given in extenso:

WOOLSTONE, SOUTHAMPTON, June 7, 1870.

MY DEAR SIR,-I hasten to send you a few prints by this evening's post (although very imperfect), to be in time for your to-morrow's meeting; but to get them ready they have been hurriedly printed on some old paper, as I had not time to obtain others; they appear discoloured. Moreover, you must look on them as only abortive attempts to see the real Podura scale under its various phases,—more especially searching for the beaded structure.

The negatives are all from the same scale, which is on a slide given me by my much-respected friend, the late Richard Beck, therefore the genuine kind; unfortunately the slide is now much overrun by mycelium threads, and one crosses the best part of this scale, that is, the part lying close to the cover, but beneath it on the surface of the slide.

FIG. 1.

I have used for the photograph marked A, Wales' and achromatic concave with a achromatic condenser, and my usual solar microscopic mirror, large and small condensers with a plate of ground glass interposed at the focus of the collecting lens. For B and C the same, with a double plano-convex condenser 1 inch in diameter, with a stop over the top lens of the shape Fig. 1, and the small lens of the solar condenser removed. For D the same as B and C, substituting a Nachet's small prism of 30° angle, and replacing the small solar condensing lens. For E and F the achromatic condenser with the large and small solar lenses, and ath made by myself-after Mr. Wenham's published formula-with an achromatic concave. The weather was

* Secretaries of Societies will greatly oblige us by writing their reports legibly -especially by printing the technical terms thus: Hydra-and by "underlining words, such as specific names, which must be printed in italics. They will thus secure accuracy and enhance the value of their proceedings.-ED. M. M. J.

Journal,

too windy to obtain sharp pictures, causing considerable vibration to the large mirror.

I will spare you a recital of the many trials I have had, and the difficulty to secure anything like the said beaded structure; and remember I have not attempted to obtain what is ordinarily supposed to be the optician's appearance;-just the reverse, everything else except the right ones you'll say, so be it.

Now the appearances recorded are most fleeting, and required the hand to be on the pinion of the horizontal and vertical adjustment of the mirror to the moment of putting the sensitized plate in its place. Unfortunately I have had sent me some miserable collodion, which would not intensify after the usual methods, so that to procure printing density I had to resort to all sorts of expedients, and on so doing secured much obscurity.

I don't think we are yet in order as regards the true structure of this scale, and fancy analogy from other scales should enter into the debate, for to describe the true structure of a transparent object by transmitted light is most difficult: not that I am going to open the question by affirmation; this I leave for wiser heads, with better appliances.

However, to start from a point, and as I shall not be hanged for thinking, I may say that the testing of the scale under very varied illumination, and my never having been satisfied with the appearances obtained by myself photographically, I fancy the following may meet my undecided views.

I take the scale to be a truly ribbed structure, finely beaded on the ribs, which deviate or undulate, approach to or widen from one another; when these undulations are focussed so as to give the approximating parts of the upper and under surfaces, you have the undulation of the ribs, converted into notes of admiration and the beading lost, except under most favourable states of illumination and perfection of the objective corrections. The undulations give the waviness, and by slight obliquity in the illumination are thrown from the ribs farther, so that diffraction comes fairly into play, and may produce anything according as the pencils traverse the scale at various angles to the undulating ribs. The prominent round beads shown at some parts of the focus at the head of the notes of admiration, may then be due to the union of the ribs at the points where the widening springs from the same, as is seen so continually in photographing objects with

FIG. 2.

large hemispherical bosses, at the bases of the apparent or made to appear hexagonal areas, when they touch each other, which is shown beautifully in a photograph of Coscinodiscus taken with Mr. Wenham's long since. See Fig. 2.

Now whether this ribbing should be considered as a true rib set at right angles to the plane of the intervening structure, and that intervening structure a single membrane, or whether the membrane be double and the rib seated on its surfaces, one on either side, or whether the ribs are exactly opposite one another,

I cannot say, but somewhat incline to the former, so that a transverse section of the scale across its length would, in exaggeration, be somewhat after these figures:

or

Single membrane.

And if you suppose these ribs carried in the direction of the length rather obliquely, and their edges not truly parallel, but waved at short intervals, as in the Figure 3, you may have almost every variety of appearance you desire under various kinds of illumination and focus:

In attempting to photograph this object I had considerable annoyance from the almost immediate loss of the forms obtained on the card screen, from which I supposed some change in the position of the little scale from the extreme heat at the focus of

L FIG. 3.

the condenser. Sometimes I fancied the scale curved from its attachment to the cover at both ends, sometimes from one, but this may have been fancy, though I can assure you both eyes and arms ached ere the day's work was over, the former close to the card with hand magnifier, the latter stretched out to the adjusting pinions of the mirror.

So much, then, for these attempts, without an "aplanatic searcher," of which I have seen no account, but which I expect will set all these hallucinations at rest, when I can obtain a peep at the object à la Pigott, who, by the way, deserves our thanks for rousing us from supposed security.

Believe me very faithfully yours,

JABEZ HOGG, Esq., Hon. Sec. R.M.S., 1, Bedford Square, London.

R. L. MADDOX.

A vote of thanks was unanimously given to Dr. Maddox for the photographs.

The President then called upon Mr. James Bell to read his paper "On Fermentation and Parasitic Fungi."

Mr. Slack said it was impossible to do justice at that moment to the very elaborate paper which had been read by Mr. Bell, as it comprehended a great number of details which could not be dealt with until it had been carefully perused. Several of the facts which Mr. Bell had adduced tended to confirm some remarks which he (Mr. Slack) had made long ago on this very subject. The Fellows would probably remember his allusions to the amazing multitude of bacterium bodies in the vinegar plant; and also the evidence which he adduced to show that this plant performed the twofold function of inducing both vinous and acetous fermentations. He noticed that Mr. Bell

had followed French writers in referring vibrios to the animal kingdom; but in this he (Mr. Slack) could not agree with him, for he had no doubt that they more properly belonged to the vegetable kingdom. If not, it was clear that the vinegar plant must be regarded as a true Zoophyte, with plant and animal organization mixed together. He wished to make an observation on the term "Catalytic action," which Mr. Bell had used. He could not help thinking that the word Catalysis had been employed by chemists to cover ignorance, and no intelligible meaning could be assigned to it. Alluding to Mr. Bell's remarks on Penicillium glaucum, in which he contradicted the opinion that it was one of the forms of the yeast plant, he (Mr. S.) did not think Mr. Bell's observations would invalidate the ordinary belief of Fungologists. He nevertheless desired to bear his testimony to the general value of Mr. Bell's paper, and the great amount of research which it displayed.

Mr. Hogg said he felt convinced that if we desired to obtain a thorough knowledge of these fungoid processes it could only be done by combining the knowledge of the chemist with that of the microscopist. But as opposed to what had fallen from Mr. Slack, he had very recently attended a lecture delivered by a learned professor of chemistry, in which the lecturer undertook to demonstrate that the yeast-cell was an animal cell; must no longer be regarded as belonging to the vegetable kingdom. He begged to thank Mr. Bell for the opportunity afforded him of witnessing the various experiments which had just been related, and which had removed from his mind some erroneous views hitherto entertained on this subject. He (Mr. H.) questioned the use of the term spontaneous generation. The term used should express the mysteriousness which seemed to surround some of these processes of fermentation, rather than that of conveying any idea of spontaneity. Many of the mysterious phenomena in experiments like those recounted by Mr. Bell, had resulted from carelessness in conducting the experiment; for instance, that of not boiling a solution sufficiently long to destroy the germs contained in it. The destructive process employed by Mr. Bell enabled him to say that nothing like life remained behind to set up further change or ferment.

Mr. Brooke said he understood the term "spontaneous generation" to mean the development of organic germs of some kind, independently of and without the pre-existence of any germ developed from organic matter. He believed Mr. Bell had used the term in a different sense to this, since he had alluded to the pre-existence of germs which produced the organisms.

The President said he understood Mr. Bell to say that he had never found one fungus pass into another. Each fungus retained its own peculiar character throughout the whole of its existence.

Mr. Bell, in rising to acknowledge a vote of thanks, remarked that he could not exactly agree with the remarks made by Mr. Slack with reference to vibrios. He was of opinion that they seemed to have a determinate object in view, and also appeared to have some powers of locomotion. They could not therefore be classed among vegetables,