i | i | “4 oN Bers ee = A eee = ‘ ra cs +* - " ~~ _ y i + & - ’ " pepo = = pert - > 7 4 . ‘ ~ -“ 7 = . ahi 3 P 2 . ) 1 a ao m 1 7 i *. - cia , - . j . = - iy 7 t . ‘. — Pt ‘ ere / { : iy } b. f ti = . — ’ | ri 2 re ; i " . Pai ca > 1 . = ; . Y? 1 4 5 ‘ . t t 3 we, co F } . * i - ‘ u “4 + . i 1 1 t , \ i ‘ . 1 ¢ a fi - ‘ { - af ! . ts, } ‘oo Ps . . . , ' a Ms 5 ‘ C a _ Y as _ < f - v ; a = . Bs } r ; eevek r 4 . oe ” : S23 Raa 5 f ‘i ; Ay fix fs 5 oy VP ows r i . ‘ ss y is . n i - 4, Z . A f ¥ + i { 7 -) “ K Es t . bo a “ bags a ioe eA ‘ a = Bom a ea 9 ===. et = 4 mer RRND eee ee 5, No. 4 showing the instrument when closed, and No. 5 as it appears when opened out for use ; and as the general plan of this is precisely the same as the one previously described, it will be only necessary for me to say that I propose to make the supporting pillars work with hinges, which are pre- vented by a catch from going out of the perpendicular; these pillars (which, in this case, are joined together at sides by two cross bars for the purpose of giving them greater firmness) are made to fit into four corresponding sockets in the stage, which is now separate from the lower portion of the microscope. Any further detail will, I think, be unnecessary, as I have only attempted to indicate how the reduction in size might be effected without interfering with the distinctive features of my original plan. On a new CoMBINED BinocuLAR and Sincote MIcroscorn. By F. H. Wenuam. (Read December 12th, 1860.) Ar the mecting of this Society in June last, I exhibited and described an improved binocular microscope, on the principle of dividing the image by means of a thin achromatic prism fixed close behind the object-glass. ‘The improvement on a former instrument (which had the defect of being pseudoscopic) consisted in refracting the right and left hand sections into the opposite eye, and by this transposition obtaining a true orthoscopic effect by an arrangement equally simple as before. Having since still further advanced the definition, by a modification in the construction of the prism, the performance was so superior to anything that preceded it, that several were made for parties who had seen the results, and which instruments proved satisfactory to their owners. It appearing evident that the use of the binocular micro- scope was likely to become general, I have directed my attention once again to its improvement, and come before you this evening on the same subject, to announce the attain- ment of a degree of success in respect to convenience, sim- plicity, and improved definition, that, considering the nature of the principle, could not have been anticipated. It is, perhaps, scarcely requisite to urge the advantage of being able to view minute organisms with the aid of both eyes together; for it is admitted that the single microscope affords but little appreciation of undulations of surface or bulk. We have even now a vivid recollection of looking through the microscope for the first time, as exhibited at the Society of Arts five and twenty years ago, by our member, Mr. Cornelius Varley. The objects were the wheel ani- malcule and the sap circulation in the Chara. Not having, at that time, the least knowledge of the instrument or objects, we formed no idea of bulk; but observing a moving object in a field of light, supposed the effect similar to the repre- sentations of a magic lantern, the then familiar toy of our youth. The living organisms revealed by the microscope still possess a charm for us beyond all others, for herein can be traced the first links in the chain of creation. Quickly pass- ing from the simple vital plant-cell to higher grades of deve- 16 Wenuam, on a Binocular and Single Microscope: lopment, we hover at length in pleasing uncertainty at the confines where the plant may be supposed to end and animal life commence. ‘The waistcoat-pocket may conceal our menagerie, and any locality furnish objects. For example, at this season of the year, draw from the nearest hedge-side ditch a rotten leaf. ‘ Drop it again,” the unknowing would say in disgust, it is decomposing, and covered with a loath- some-looking slime; but remove a portion of this, and place it under the microscope, and marvellous is.the living host displayed to view, consisting of Diatomacee, Desmidie, Oscil- latoria, Amebe, Rotifers, &c., all assembled together in one dense crowd, perfect in beauty and cleanliness. An hour may pass away unheeded, im the interest caused by observing the movements of these creatures ; but greatly is that mterest enhanced by the aid of binocular vision; they appear then not as mere moving discs, but in all the reality due to life and substance. The chief inconvenience of all the binocular microscopes hitherto made, besides distorted or imperfect definition, has been the necessity of a separate double body ; and the con- stant trouble of shifting this for the smgle tube very much limits their utility. There is also the difficulty of cleaning the prisms, and a liability to their derangement. In the in- strument I have now to describe these objections do not exist; for the effect, as a single microscope, is not in the slightest degree impeded or interfered with, and by a touch of the finger it is instantly converted into a bmocular, or back again. The annexed diagram will explain the principle of action; a is the body of an ordinary microscope, moved perpendicularly relative to the stage, with fine motion, &c., precisely as it is commonly made. On the right-hand side, in the neck at B, is cut a square hole, through which a prism, c, having two reflecting surfaces, is made to slide, as close behind the object-glass as possible. This prism is held by the ends only in the sides of a small drawer, so that all the four polished surfaces are accessible, and should slide in so far that its edge may just reach the central line of the ob- jective, and be drawn back against a stop, so as to clear the aperture of the same altogether, in which case the tube 4 acts without impediment as a single microscope. When the prism is thrust in more or less, it collects a portion of the rays and reflects them to the opposite side of the tube, at D, where an opening is to be made large enough to admit them all, under extreme conditions. Parallel with the direc- tion of these rays is “ grafted on” the supplementary tube -E, with eye-pieces, &c., and in size corresponding with the WenuaM, on a Binocular and Single Microscope. 17 main tube. The additional body may either be soldered permanently on to the other, or be made to draw on and off, a double collar holding them together at top, and a clip or bolt Fig. 1. at the bottom. In the latter case, when the inclined tube is re- moved, a cover should drop neatly into the aperture, flush, and be secured by a bolt. But the additional body beimg no hindrance to the ordinary action of the microscope, it is best always to allow it to remain in place ready for instant use, as required. When the prism is drawn out to its limit, the main body acts just as the usual single instrument, and therefore needs no explanation ; but on thrusting it in, a part of the rays are thrown into the eye- piece of the inclined body, and thus the right-hand rays of the object-glass are reflected mto the left eye, and the remainder pass directly into the right eye, having nothing intervening to obstruct them in the due performance of their best effect. The prism need not, in all instances, be thrust in to its fullest extent, so as to take in the total half of the object-glass, but only partially, to the degree requisite for throw- ing the object up in relief. In the case of a difficult test the largest share of the direct aperture may be employed, while, by coaxing the illumination for the reflected portion, the instrument can be made to perform well on the diato- maceous tests. With respect to the illumination, in all cases where pos- sible the opaque principle should be employed, as it gives to objects a far more natural appearance. When transmitted light is needed, a large, angular pencil should be used, other- wise the two fields cannot be equally lighted with the higher powers. I intend to have a split mirror made, each half capable of separable and independent adjustment for each body. The necessity for this will be shown with the Podura, VOL. I, NEW SER. b 18 Wenuam, on a Binocular and Single Microscope. for on bringing out the markings with the maximum dis- tinctness for the reflected vision, the direct will be found deficient. On altermg the mirror, equal distinctness can be obtained in the direct tube, at the expense of the other. If each tube, therefore, has its own independent mirror, this inconvenience will be obviated. The adjustment for difference of distance between the eyes is effected as before, the draw tubes being at the minimum limit of proximity when close in, and by drawing these out to a small extent they accommodate for all positions of eyesight. ‘This answers so well in practice as to need no amendment. It will be seen that the reflected rays have further to travel to reach the eye- piece (the radius of each tube being the same). The distance is just equal to that which they have to traverse across the interior of the prism; this causes a slight disagreement of focus between the two, which may be compensated for by drawing out the main tube about a quarter of an inch more than the other, but it would be preferable to make a small difference in the mag- nifying power of the eye-pieces, which can be simply done by an alteration of distance between their lenses, each eye- piece to be marked for its appropriate tube. By transposing them such an adaptation would often compensate for those whose eyes differ materially in focus, or one being long and. the other short-sighted, which is a common defect. The base into which the prism slides rotates to a small extent, for reflecting the image level with the centres of the eye-tubes ; this is the only adjustment, and when set right 1s held fast by a binding screw in the side of the inner fine motion tube. The prisms having two opposite reflecting surfaces, possess the common property of such, that, how- ever much tilted, the direction of the ultimate emergent ray cannot be altered. Great care and nicety is, therefore, need- ful in working them to the exact angles for the definite direction in which the ray is to be finally reflected, but this having been properly obtained, gives the double-reflecting prism this advantage, that it cannot be readily put out of adjustment. Fig. 2 is an enlarged outline of the prism; a ray of light, a, passing through the base, is totally reflected by the surface, B, towards c, at which surface it is again totally reflected in the direction required. Both the inci- dent and emergent surfaces of the prisms must be perpen- dicular to the direction of its corresponding ray, as any refraction is objectionable, and the reflecting sides be ar- ranged considerably within the angle of total reflection (which, for crown glass is about 48°). ‘The base of the prism Wenuam, on a Binocular and Single Microscope. 19 should be of a width only just- requisite to include the half aperture of any object-glass, one quarter of an inch is quite sufficient; it should not exceed this Fig. 2. for two reasons, first, that the greater the thickness of glass that the ray has to pass through, the more difference there will be in the magnifying power of the two bodies, and second, that a thick prism takes the ray more away from the centre of the main tube, and increases the convergence of the two, bringing the eyes nearly approaching to the dis- agreeable condition of a squint. Both the transmitting and reflecting surfaces of the prism should be accessible for the purpose of wiping, for any par- ticles or mildew adhering to the latter will prevent total reflection at the point of contact. If the prism is well made and polished, and of the smallest size possible for admitting the pencil, the difference between the direct and reflected ‘ image is scarcely appreciable, and with this standard of com- parison a faulty prism will immediately be detected. By pressing back the spring catch or stop on one side of the prism-slide, it can instantly be withdrawn altogether, and as quickly replaced. 20 On Cuanczs of Form in the Rep Corruscites of Human Bioop.—By Wiiiiam Appison, M.D., F.R.S. (Communicated by Dr. Lankester. Read December 12th, 1860.) WueEw freshly drawn, human blood is examined with a microscope, the form in which the red corpuscles appear is well known. The greater part of these bodies adhere together in rolls, a few floating singly in the blood-fluid, or liquor sanguinis. (Plate ITI, fig.1.) We may call this form the normal form. But occasionally, without anything having been added to the blood, the forms depicted as alkaline forms (fig. 2) may be seen. These rough or prickly forms (fig. 2) are with certainty produced by fresh urine, by a weak solution of common salt, and by various liquids rendered slightly alkaline with solution of potash. On the other hand, the forms represented in fig. 3 are determined by adding to the blood a solution of sugar and liquids rendered feebly acid by hydrochloric acid, or by lemon or orange juice. The tailed forms (fig. 4) occur when blood is submitted to the action of sherry wine. Make a saline solution by dissolving one grain of common salt in two fluid drachms of water, and render it very slightly alkaline with solution of potash; also dissolve four grains of refined sugar in two fluid drachms of water, and render it slightly acid to litmus paper with the diluted hydrochloric acid of the London Pharmacopeeia. Receive a small drop of fresh blood upon a slip of glass, and place near to, but not touching it, a similar amount of the saline alkaline solution ; also place in a like manner, on the other side of the blood, an equal quantity of the acid-sugar solution; drop down upon the three fluids a thin piece of glass, so that the alkaline fluid may come into contact with one side of the drop of blood, and the acid fluid into contact with the opposite side of it. : Upon examination with the microscope, the forms of the corpuscles which float out into the alkaline fiuid will be found quite different from those which float out into the acid fluid. Those in the alkaline fluid have roughened outlines (fig. 2), whereas those in the acid liquid have smooth outlines, and a bright matter, of sundry forms, makes its appearance in their interior (fig. 3). If the corpuscles be followed as they continue Avpison, on Blood-corpuscles. 21 to float out in the two fluids, we find them experiencing further, but different, changes of form. In the alkaline fluid the phases A,B, fig. 2, and in the acid fluid the phases c,p, 8, fig. 3, will be seen. Again, take a small drop of blood and place close to it an equal quantity of the alkaline-saline liquid, drop down upon them a thin piece of glass, and when a mul- titude of the corpuscles have floated out into the fluid and have assumed forms fig. 2, add at an edge of the covering- glass a drop of the diluted hydrochloric acid, and these forms will be seen changing into the forms fig. 3. Lastly, take a drop of blood and place near to it an equal amount of the acid-sugar solution, let fall upon them a thin covering-glass, and after a little time numerous corpuscles will be found of the forms represented fig. 3, add at an edge of the covering- glass a drop of liquor potasse, and forms fig. 3 will alter into forms fig. 2. The changes described may take place quickly or more slowly, according as the added fluid flows with more or less rapidity; in the latter case it will be remarked that the corpuscles in progress of change from one form to the other regain for a brief space of time their normal figure and appearance (fig. 1). We are able, then, by an appropriate appli- cation of alkaline and acid fluids to impress particular forms upon the red corpuscles of human blood, and we see them during the transition from one form to another regain their normal characters and aspect. This property of change of form in the corpuscles of the ‘blood is not of long duration, it remains with them but for a limited period after their withdrawal from the circulation, and some of the corpuscles appear to lose it sooner than others, for, after a little time, corpuscles of different forms are to be seen floating side by side in the same current, and the further addition of an alkaline or acid fluid destroys them, without inducing any further change of figure. We have called forms fig. 2 alkaline, and forms fig. 3 acid forms, not because they are exclusively determined in the one case by alkaline and in the other by acid liquids, but because the alkali.potash will change the normal form fig. 1, and also forms fig. 3, into the forms fig. 2, and, again, because the hydrochloric and other acids will alter the nor- mal form, and also the forms fig. 2, into forms fig. 8, when they are properly applied. In repeating these experiments, it will be seen that cor- puscles which approach near to an edge of the covering-glass, whatever may be their form, lose thereby all power of fur- ther change. Now forms 4, fig. 2, which result from contact with alka- 22 Appison, 0n Blood-corpuscles. line and saline fluids, are hke forms d, fig. 3, which are pro- duced in acid liquids, the only difference between them being that those observed in alkaline are deeper coloured than those in acid fluids. Corpuscles of this form 6, fig. 2, and d, fig. 8, are incapable of regaining the normal form. UlIti- mately, in alkaline fluids, the forms 0, fig. 2, burst open, and the corpuscles are wholly dissolved; im acid liquids (fig. 3, d) they sometimes burst open suddenly, and some- times suddenly increase in size, the contents of the corpus- cles become colourless, and the enlarged capsules, with a granular matter within them, have very much the appearance of the white corpuscles of the blood (fig. 3, e). Dissolve a grain of common salt and half a grain of bicar- bonate of soda in two fluid drachms of water, mix this solution with half a fluid ounce of good sherry wine, and filter. This liquid produces the tailed corpuscles (fig. 4). A small drop of blood and an equal quantity of the vino-saline mixture must be placed side by side on a slip of glass, so that their edges may mingle when a thin covering-glass 1s dropped upon them. In about five or ten minutes numerous corpus- cles, where they have floated out in the liquid, will be seen throwing out matter from their interior, two, three, four, or more minute molecular particles frmging their circum- ference. Some of these molecules separate from the cor- puscles and float in the fluid, others elongate into tails, which wave about with a tremulous motion, in a very remarkable manner. ‘These tails all have a little knob at their extremity. After a short time, or upon any motion in the fluid, the tails break away from the corpuscles, but their singular move- ments do not cease when this has happened. Sometimes a discoid enlargement forms on some part of the tail, and then the tail suddenly retracts itself into a larger granular and coloured particle. That the movements of these tails are of a peculiar kind, and not due to motion in the liquid, is shown by this—that all movement in them ceases entirely when they approach near to either of the edges of the covering, thin glass. In repeating this experiment, if the surfaces of the upper and under glasses come so close together as to press upon the blood-corpuscles—which is known by increase of their diameter—the tails will not appear. The corpuscles must be free from pressure, for the effects described to take place. Moreover, tails are not readily produced if the stand of the microscope and the glasses are cold; the phe- nomenon takes place much sooner, and the tails are longer, when the instrument and fluids have been for some time in a warm room. Appison, on Blood-corpuscles. 23 The following have been found to succeed in producing the tailed forms of corpuscles (fig. 4) : 1. Sherry wine. | 2. Sherry wine and saline solution. 3. One part fresh urine and two or three parts sherry wine. 4. Port wine and quinine.— Dissolve with a gentle warmth one grain of sulphate of quinine in half a fluid ounce of port wine; set it by for two or three days, and then filter the liquid. 5. A mixture of the sherry wine and the saline solution with port wine and quinine.—This mixture seems to improve by keeping. The following experiments have been tried : 1. One fluid drachm of the mixture No. 5 and one grain of sulphate of strychnia, shaken together.—Tails produced. 2. One fluid drachm of No. 5 and one grain of acetate of morphia.—Tails produced. 3. One fluid drachm of No. 5 and liquor potasse, just suf- ficient to remove the acid reaction of the mixed wines.—No tails appeared. In all these experiments there is no mixing together of the blood and the extraneous fluid previous to the application of the covering-glass, hence there are various degrees of inter- mingling between the added fluid and the natural fluid of the blood, and it is only where these two fluids are mixed in cer- tain unascertainable proportions that the specific phenomena are to be seen. Blood consists of a fluid—the liquor sanguinis—and the cor- puscles ; therefore, before arriving at any conclusion from the preceding experiments, it will be necessary to consider the part played by the fluid element of the blood. The added fluids, when they come, undiluted by the liquor sanguinis, into contact with the red corpuscles, destroy them. The changes of form of the corpuscles are therefore effected, not by the extraneous or added fluid alone, but by a mixture of the added liquid and the liquor sanguinis; and we conceive it to be correct to regard the phenomena described as the results of a change in the quality of the liquor sanguinis, wrought by the added liquor. It is to an unascertained mixture of the extraneous fluid and the natural blood-fluid that the various aspects of the corpuscles must be ascribed. It is well known how speedily elements of diet, medicinal substances, and poi- sons, are found in the liquor sanguinis, and these experiments show that corpuscles which have been changed in their form from change in the quality of the liquor sanguinis may be altered back again to their normal form by a counteracting 24: Appison, on Blood-corpuscles. agent. But before any actual change of figure in the cor- puscles occurs, we must suppose a disposition to the change, and therefore we may conclude that such a disposition may be removed by an appropriate—a counteracting agent. Lastly, we regard the facts as substantiating the doctrine that the fluid element of the blood has a pathology distinct from that of the corpuscles. TRANSACTIONS. Report on Surprs or Diaromacem, mounted by EK. SAMUELS, for Boston (U.8.) Socimty or Naturau History, and presented to the Microscopicau Socizty or Lonpon. By CHARLES STODDER. | (Read October 10th, 1860.) Tue diatoms of our coast have been but little studied. These specimens will, on that account alone, possess consider- able interest, though they have only been glanced at, for want of time. Those from Quincy appear most promising. The Milton slide contains almost entirely what Mr. Samuels con- siders a new Himantidium. The Bangor and Bemis Lake deposits are similar to other “‘sub-peat” deposits found all over New England, and described by Ehrenburg and Bailey. These have not been fully studied as yet. The diatoms from the intestines of Holothurians and Echini are of great interest. They were taken from animals col- lected for our members, Mr. Jas. M. Barnard and Professor L. Agassiz. Some of the slides, prepared and mounted by Mr. Samuels, coming into my possession last spring, I - noticed that they were very rich in genera and species, and that many appeared to be new. I sent specimens to our corresponding member, Mr. A. M. Edwards, of New York, who has paid much attention to this department of science for several years. His interest was excited by the specimens, and a larger quantity of the material was procured from Mr. Samuels, and also some directly from Mr. Barnard, and cleaned by Mr. Edwards, which, although but partially investigated as yet, has yielded a rich harvest of new forms, as well as many but recently published in Europe, together with a great number of old and well-known species. The discovery of this source of supply of diatoms will yield important scientific results. We obtain specimens from localities otherwise all but inaccessible to the microscopist. We have ascertained that a great many species are common VOL. I.—NEW SER. c StopDvER, on Diatomacee. co) Od to the Sandwich Islands and to the Mediterranean; some species are found in the Sandwich Islands and the coasts, England, France, Nova Scotia, and Botany Bay ; some com- mon to Sandwich Islands, Zanzibar, and Florida. Diatoms have been long known as the most cosmopolitan of all organism. ‘The information afforded by these slides adds very much to our former knowledge of this character. They seem to exist as species, almost independent of climate or locality. Mr. Edwards has undertaken to make a list of the Sand- wich Island forms, and to figure and describe the new species, with the view to publication by our society. I have ex- amined these slides, prepared by Mr. Samuels, and have registered, with “ Bailey’s indicator,’ some of the new species of Mr. Edwards, as he has communicated them to me verbally or by letter, with his provisional names. These slides have not been seen by Mr. Edwards, and I only am responsible for any errors or mistakes. Mr. Edwards’s new species are— Synedra magna. » _pacifica. Triceratium circulare. id elegans, with 3 and 4 sides. % undatum, with 3, 4, and 5 sides. These variations in the number of sides revive the question whether there is any generic distinction between Trice- ratium and Amphitetras. Mr. Brightwell has described several species of four-sided Triceratium, and the only dis- tinction I can make out between 7. Wilksii and Amp. Wilksii of Har. et Bai. (‘ Proc. Phil. Soc.’) is the number of sides. Among the rare or recently described forms in the Sandwich Islands, are T. dubtwm (Brightwell), found also on the coast of Florida, Cocconeis fimbriata (Brightwell), Biddulphia reticulata (Roper). The Campylodiscus figured by Brightwell, in ‘Jour. Mic. Soc.,’ as C. striatus (Ehrenberg), is abundant, but bears but little resemblance to Ehrenberg’s description or original figure. I propose to call it C. Brightwellii. Synedra undulata, Greg. (= Toxarium undulans, Bail.), is abundant, also, at Quincy, Mass. ; so is S. Hennedyana, Grey. The two specimens have an expansion in the middle, but one is straight, the other undulated; now, we have likewise two forms, rather rare, one straight, the other undulating, but without the expansion: are all four one species? Navicule of the type of N. didyma are p'entiful; some appear identical with described species, but they are so variable that they StoppER, on Diatomacee. 27, recall Dr. Gregory’s query, whether they should not all be considered one species. The same observations apply to Navicule of the type of N. lyra. There are two forms of Ehrenberg’s genus Actinocyclus, called by most authorities Hupodiscus ; one resembles EZ. sparsus, Greg. HE. tenellus, Bréb., and the Actinocyclus of Ehrenberg (‘Mic. Geol.’ Taf. i fic. 5,c.10). Also Coscinodiscus lune (Tab. 35a, group xxi, fig. 7) ; Cos. gemmifer (Tab. 35a, group xxu, fig. 3). This form is distinguished by rays composed of lines of contiguous dots, with other dots irregularly scattered between the rays. The number of rays 18 very variable, from six upwards ; sometimes the rays are so crowded, that the jnter- mediate dots almost form continuous rays, only distinguish- able by their irregular distance from each other; colour, usually some shade of brown. The other form of Actinocyclus has very fine lines for rays, not always continuous; and the whole surface of the disc is covered with a very fine network of, probably, hexagonal markings, too fine to be well made out with my instrument. This form is represented by Eupodiscus fulvus, W. Sm., and possibly by H. subtilis, Ralfs; by a great many of Ehrenberg’s species, ‘ Mic. Geol.,’ Tab. xviui, fig. 8, c. 18, Richmond, ” Wie, SEVEN PT. 22. fies. 7, . ¥ » | ¥&kV,A, oY. 117, fig. I, and 2, enatio; » »? ”» gr. 18, fig. 1.25 and 3, guano, Saldanha Bay ; also Strafford Cliffs and Rappahanock Cliffs, var. colour, usually blue or purple, sometimes brown, and sometimes colourless. Both of these forms have generally, but not always, a nodule or process near the margin, resembling the “feet”? of EHupodiscus and Aulacodiscus ; which is probably the reason of their having been taken for Eupodisci, though the structure of the valve appears entirely different from the true species of that genus. Ehrenberg does not figure or describe the nodule, but on examining the Actinocycli of Saldanha Bay, in the Bailey collection, received, I believe, by Bailey from Ehrenberg, I find the nodule is present in them. Ehrenberg’s figures are sufficient to mdicate the genus, but not the species, except by the number of the rays, which is not a good specific character, neither is colour. But I am well satisfied that many of the so-called Eupodisci are Ehrenberg’s Actinocyclus ; in fact, it is almost admitted by Smith. These two forms of Actinocyclus should probably be placed in two genera. They have quite a different structure; that. of the first-mentioned is not cellular, but the dots are pro- 28. STODDER, on Diatomacee. jecting papille or tubercles, as may be easily seen in oblique examples. The whole group of Actinocycl and Hupodisci requires revision, and I believe that Mr. Edwards intends to undertake the task. We have quite abundant and variable Stauroptera aspera, Ehr. = Stauroneis pulchella, W. 8S. Ehrenberg made a sub-genus of those Stawroneis that were striated or marked ; but improved instruments having shown that all the Stauro- neis are marked, and none smooth, the sub-genus should be cancelled, hut the original specific names should stand. There are a great many species of other genera, some of which will undoubtedly prove to be new; but these are not worked up as yet, or I have not received Mr. Eidwards’s results. ‘There are also several new forms, whose position in classification is as yet quite doubtful. The Sandwich Island slides in this parcel represent very well the character of all the others examined, except perhaps in the genera Nitzschia, Amphora, and Campylodiscus, which have been found much more abundant in number and species than here, some of the species of which will probably prove to be new; spicules of sponges are very abundant. On the Zanzibar slides I have seen two specimens of an Auliscus, probably new; and several of an Isthmia, certainly SO. a MICROSCOPICAL SOCIETY. ANNUAL MEETING. February 13th, 1861. ¢ e e Dr. Lankester in the chair. Report or Counctt. AccorpDING to annual custom, the Council have to make the following report on the state and progress of the Society during the past year. The Society at present consists of— Compounders” - - - Al Annual Subscribers - - 259 Honorary and absent - 5 giving a total of - - 2 305 for the number of members this day on the books; of these 35 have been elected during the past year, and are included in the above number. The Council have to regret the loss by death of 5 members—P. W. Fry, Esq., Geo. Jackson, Esq., Rev. David Laing, Charles May, Hsq., and Dr. James Forbes Young. Three of these, viz., Mr. Fry, Mr. Jackson, and Dr. Young, were among the original members who founded the Society. The Council have also received seven resignations. During the past year the Library has received an accession of 73 books ; of these 25 consist of various complete works, many of which are of great value: among these may be particularly noticed the works of Leuwenhock, 2 vols. 4to., and Swammerdam’s ‘ Historia Insectorum,’ 3 vols. fol., presented with other works by Dr. Millar, and the valuable contributions of the Hackney Microscopical Society, presented through Mr. Roper; four works also have been purchased with the Library Fund; and the remaining works consist of serial publications, presented by the various editors, with the exception of one, the ‘ Annals of Natural History,’ which is purchased, as it appears, for the use of the Society. The cabinet of objects has received an accession of 66 slides, including 27 from the Boston (U.S.) Natural History Society, 14 from Dr. Carpenter, being specimens of Polyozoa “sLozIpnyy ; T9605 oe che Si S61.yh2” S (0°01 2 0 ble” ape tee So 02 0 S 19 98° = 2 QS ot 6 Cl ser: Ne ade eee i 0 0 ee 0. ies / eae ee Cox ‘oSvysod ‘Kromorye4s “{10) e TAVHNGM “HW “INVA AUNT "Pe “SG GPF Uo onp 4sosoqur s.deok BSI O1Ot[} Je] 94RYIS 04 OSTe puUe “YooI100 9q 0} WO} punoy pue ‘sioyonoa pue syueuNo0p of} Y}IM ‘syunoddE SAoMseely, oY} peulmMexo oAvy ‘paUsisdepun oy} “44 "LOST ‘Aumnugagy ¥2g spuvy Sdamnsvoly, Ul souRyeq S[OSUOD ‘PQ “SGT GEF Jo gsvyoing | e e e e . “SENTIUAY 7 £1 9688 Our ung | soyON pure voy, sosuodxa Aq10q | * puny Areaquy sosuedxa a91t0g "86 COGF vo uolssimmMoy eQ) Oiee = 3 : 3 S}OYO"} 9pttog =“ * Syatoog Avy PO SB reO se ; : er ee go Pes O}}IP JO S10ITDHT On Lf 4/2 suorydisosqng sjeumor Jo ATOATpo(T ) ol oS pajseaut suorisodiuog 1O}e.ING = 0. £ESS + : * SIOQUIOU Jo Sao} dUBIYUGT frejos90qg Jurysissy Jo Arvpeg {gq | OT OL SG : : Jeak Sv] Jo souvpeg 2 “SLAIMO LY, | 30 “TOST ‘eT AUVOATAH YT OF ‘OO8T re AQVOUGA A WOd iy LUOdaAy SUOLIGNAV The President’s Address. 31 and illustrations of the development of Comatula, and some micro-photographs by the late Mr. Jackson. At the first meeting of the present session an elaborate report was made by a committee, consisting of Mr. Farrants, Mr. Lobb, and Mr. Legg, appointed to examine, arrange, and report upon the objects in the cabinet. This task has been performed by these gentlemen in a most satisfactory manner, as may be seen by the report; and the result of their investigation is, that at the date of the report, October 3, 1860, the cabinet contained 832 objects, which for facility of reference they had arranged under 13 heads or classes, distinguished by the capital letters from Ato M. They atthe same time made a suggestion as to an arrangement by which the objects might be allowed to be taken out by the members under certain regulations, to which arrangement the Council have given their assent. The Journal has continued to be published regularly, and circulated as usual. The President then delivered the following address : The Presipent’s Appress for the year 1861. By Professor Joun Quexert, F.B.S. GrENTLEMEN,—Before proceeding to the general business which usually occupies the attention of the members of the Microscopical Society on this, the evening of the anniver- sary, | have much to say to you in the way of apology for my seeming neglect in never having occupied the chair, to which, unknown to me, I had been elected by the Council. Feeling that the state of my health did not allow me to perform the duties of the office in such a manner as I could wish, I did all in my power to prevent the appointment when it was hinted to me as likely to be made. Not having. been consulted in the matter, nor officially formed of the itention of the Council, but hearing through a private source that I had been proposed to fill the office of Presi- dent, I wrote a letter to the Council, telling them that, had my health permitted, I should have felt much honoured by the appointment; but that, as things stood, I must neces- sarily decline it. In February last, however, and but a few evenings before the Anniversary, I was, for the first time, officially informed that my letter, declining the position of 4 The President’s Address. O39 President, had come to hand too late; and that the election must stand good. I regret to say that my apprehensions with regard to the state of my health have been more than realised ; for, without a single exception, from the time of the soirée, which was held in this room in April of the past year, I have been prevented, by illness, from attending any of the meetings. Knowing, as you all do, the part taken by me in assisting to establish this Society in the outset, and that I have per- formed the duties of Secretary for a period of nineteen years, during many of which I was unassisted, my declining so honorable a post as that of President must, at first sight, have given rise to-the idea that either my views as to the usefulness of the Society had changed, or that my occupa- tions, being numerous, would not allow me time for micro- scopical investigation, nor for the transaction of any business connected with the Society ; but when I state the truth, viz., that I have been physically incapable of performing these duties, I feel sure that no further apology will be needed, more especially as I endeavoured in every way to prevent my appointment, having, on more than one occasion, previously refused it on the same grounds. I can only add, that should it please the Almighty Disposer of events that my health should be restored, I shall hope to be able, at some future time, to show you that a long period of unavoidable absence has in no way diminished my love for this Society, nor the zeal and energy with which I once assisted in carrying on its affairs. Since the Anniversary, which was held on the 8th of February in the past year, there have been nine meetings of the Society; and, in addition to the subjects which have been brought forward orally, no less than thirteen papers have been read; and of these, four relate to the Diatomacee, a subject which, perhaps, more than any other, has, from the earliest days of the invention of the Achromatic Micro- scope, occupied the time and attention of the most persevering and painstaking portion of our Microscopic community ; “a certain number occupying themselves with the nature of the markings on the surfaces of the valves, whilst others are engaged in classifying and arranging the numerous spe- cies which are daily being precured from all parts of the habitable globe. We are indebted to Dr. Greviile, Dr. Wal- lich, Mr. Norman of Hull, and Mr. Tuffen West, for these papers, all of which have been published in full in the ‘ Tran- sactions’ of the Society, and many of them have been de- lineated by the accurate pencil of the last-named gentleman. The Presidents Address. 33 The paper by Dr. Greville is a very elaborate one: it is en- titled a “ Monograph of the Genus Asterolampra, including Asteromphalus and Spatangidium.’’? The material employed for investigation was obtained from three very different sources ; the first consisted of soundings from the Indian Ocean ; the second, of a deposit from the United States, prepared for examination by Mr. E. W. Dallas; and the third, of a substance known as the Monterey Stone, prepared by Pro- fessor Walker-Arnott. One great object of this paper is to point out how far the genus Spatangidium of De Brébisson should have been adopted in his former paper; the species formerly described as belonging to this genus being consi- dered as strictly referable to Asteroiampra or Asteromphalus. The paper by Mr. Tuffen West is entitled “Remarks on some Diatomacez, new or imperfectly described, and on a new Desmid.” The sources from which the algze upon which Mr. West’s observations have been madewere various, some of them being from the British coasts, others from the Mauritius and from the so-called Barbadoes earth. The genus Triceratiuimn is the one principally mentioned; and of this no less than seven species are described, and figures of each given, with the usual accuracy of this accomplished artist. Five other genera are then alluded to, and one or more species of each described of these genera; that of Aitheya is new, and its species A. decora was found by Mr. Atthey plentifully on Cresswell Sands, in June, 1859, and in May, 1860, in Druridge Bay. At first sight this species 1s con- sidered to resemble Striatella unipunctata im miniature ; but the presence of spinous processes at the angles, and the entire absence of stripes or attachment of any kind render the establishment of a new genus perfectly necessary. The paper of Mr. Norman, read in June, is a continua- tion of that brought before the Society in January, 1860. It is a list of the various forms of Diatomacee in the neighbour- hood of Hull. The genera Pinnularia, Stauroneis, Pleuro- sigma, Synedra, Gomphonema, Meridion, and upwards of thirty others, are represented each by one or more species, tending to show not only the richness of the locality, but also the zeal, activity, and powers of discernment of the microscopists of that town in this particular department of scientific inquiry. Volvox globator, which within the last few years has occu- pied so much of the attention of microscopical observers, has points in its history still remaining to be cleared up. Dr. Hicks has done much to make the matter clearer, and has pointed out a stage, viz., the ameeboid, in which this Protean 34 The Presideni’s Address. form agrees with that of three other members of the veget- able kingdom. At the same meeting, Dr.Wallich, in a paper, entered into a discussion on the structure of the diatom valve; believing, from his observations, that the growth of the valve ceases either at or shortly after its liberation from the parent. That, subsequently, no change in shape occurs im the siliceous valve except at its margins. That the mark- ings are circular, and arranged determinately according to species; the figure being dependent upon forces occurring during its connection with the parent frustule ; the size and relative fineness of markings depending upon the condition of the frustule while in the stage of generation. As to the gelatinous envelope, its growth may probably go on in- definitely. The next paper relates to the zoophyte division of the animal kingdom. Professor Allman described, in a paper read 14th March, 1860, a new genus of Lucernaride, Carduella, identical with the species L. cyathiformis of Sars, but differmg from the true Lucernariide in the margin of the circular disc not being produced into the rays, the tentacles not springing from the edge of the cup, and in these being situated in a single circle. From a careful description of its anatomy, he believes it to represent a true hydrozoan type, notwithstanding a resem- blance to the actinozoan,in the presence of the vertical lamellze connecting the stomach with the outer wall of the animal. The papers relating to the improvement in the microscope itself, and in the apparatus connected with it, have been, during the last year, more numerous than in any preceding one. Thus, there have been two on the Binocular form, by Mr. Wenham; one on a Portable Field or Clinical Micro- scope, by Dr. Lionel Beale; and another on a Dissecting Instrument, by Mr. James Smith.~ All these are fully de- scribed and illustrated in the ‘Transactions,’ and are worthy of the greatest attention from their being the contrivances of men qualified in every possible way to show to the uninitiated what is truly good and useful. Mr. Wenham’s invention, however, is one which requires more than a passing notice, as it is likely to prove of greater use to the observer than any other form of instrument which has yet been brought before the notice of the members of this Society ; and glad should I be if the limits of this address would allow me to enter fully into some of its advantages. The next duty I have to perform is a painful one, viz., to remind you that although our little community scarcely —- The President’s Address. 39 numbers three hundred strong, yet within the last year no less than five of our members have been taken from us by the unsparing hand of death. These are James Forbes Young, Charles May, David Laing, P. W. Fry, and George Jackson ; and of all the losses the Society has met with since its formation, no greater one has happened than that of so valuable a member as Mr. Jackson, for there is hardiy one amongst us who has used the microscope as a scientific instrument, but has been more or less indebted to Mr. Jack- son’s skill for the imstrument employed im taking accurate measurements of minute objects. Mr. George Jackson was the eldest son of a farmer at Higher Yellington, in South Devon, and was born in 1792. At an early age he exhibited a strong mechanical genius ; his first attempts in that direction being to manufacture a mouse- trap, his grandmother having promised him a guinea for the first that was caught, under the impression that sucb a thing was impossible ; a mouse, however, was soon trapped, and the promised guinea as quickly reduced to a half-crown. Then sixpence a head was the price affixed; but still, even at this reduced rate, the money earned fiom the efficiency of the trap was considered too much for so young an artist, and payments consequently ceased altogether. He was educated at the Ashburton Grammar School, whither his innate tendencies, also followed him ; and if ever young Jackson was missing, he was sure to be found in the workshop of Mr. Ireland, the carpenter. Numerous lasting memorials of his skill, in the form of writing-desks, work-boxes, &c., still remain to evidence this early predilection. | Mr. Jackson was articled to Mr. Gervis, a surgeon and medical practitioner at Ashburton, whose sons had been his schoolfellows, and whose second daughter he afterwards married. He attended the lectures at the United Hospitals of St. Thomas and Guy, and took the diploma of Member of the Royal College of Surgeons of London in 1813. At an early period of his life he was an excellent manipu- lator with the table blowpipe, and supplied himself and many of his relatives and friends with most excellent thermometers, hydrometers, and barometers. He also constructed a transit imstrument, which was erected, when in use, on a stone cantilever firmly embedded into the wall behind his house. In 1826, he was rewarded by the Society of Arts for an ingenious and useful instantaneous light-apparatus, being a modification of the hydrogen and spongy platinum lamp. Mr. Jackson was an early lover of the microscope, and many years before the existence of our Society constructed a very 36 The President’s Address. efficient instrument for using the doublet lenses introduced by the late Dr. Wollaston; the two lower pairs of these he framed and figured for himself. This was followed by the pro- duction of a large-sized imstrument, capable of effecting all that the best microscopes of that period were able to do. At the turning-lathe and planing-machine he was a thorough workman, and these instruments he had constructed on his own plans, and much of them by his own hands. He was the first to show the great importance of employing the latter for perfecting the instrument and economising labour. Mr. Jackson was one of the original members of our Society at its formation in 1840, and most of his various suggestions for the improvement of his favorite instrument have been laid before the members. | The first of these was a paper “On Microscopic Measure- ment,” read September 23d, 1840, and printed in the ‘ Micro- scopic Journal,’ vol. 1, p. 1l—a subject with which his name has become so intimately connected. In April, 1841, he described a portable candle-lamp for illumination by reflection, some observations on ‘which will be found in the ‘ Microscopic Journal,’ vol. ui, p. 77. This was followed in November, 1847, by his paper on “ The Eye- piece Micrometer,” published in the ‘ Transactions of the Society,’ vol. n, p. 134. The small but elegant little ruling-machine, which he con- structed for the division of these micrometers, is a most effi- cient arrangement, and although, I believe, never figured or described, yet he had no hesitation im exhibiting it to any person who was interested in such matters. It was about this period that he also constructed a very complete and serviceable cutting-machine for producing thin sections of woods, &c. In 1852 Mr. Jackson was elected President of this Society, and I am sure that the members will all bear witness with me in stating that he was at all times most active in advanc- ing the true interests of the Society. In conjunction with Dr. Carpenter, Dr. Lankester, and your President, he was appointed by the Council of the Society of Arts a member of the committee, to assist in awarding their premium for the best and cheapest microscopes. In May, 1857, he exhibited and described a new form of travelling microscope, four of which he has constructed as presents to various relatives. Soon after the process of photography on collodion had become practised, Mr. Jackson turned his attention, with his accustomed clear-headed assiduity, to this engaging branch of The President’s Address. 37 art, constructed for himself a camera box, travelling arrange- ments for micro-photographs, and with a good achromatic lens, manufactured by Ross, set to work with his usual per- severance and industry to take the portraits of all his relatives and friends, scientific or not, the liberal distribution of which among his large circle of acquaintances afforded him un- alloyed pleasure. The Society’s museum is enriched by his liberality with micro-photographs of some sixteen of its members. Several other short notices from our deceased member have also appeared in the pages of the ‘ Quarterly Journal of Microscopical Science,’ as On thin glass Covers” (vol. 1, p. 141), “On Micrometers and Micrometry”’ (vol. iv, p. 241), “ On Microscopical Photographic Portraits” (vol. vu, p. 122). He also undertook to oblige his friend, the late Dr. Pereira, with the measurement of the starch granules of various amy- laceous substances for the last edition of his ‘ Elements of Materia Medica’ then in preparation, twenty-five of which have been published in that work. One of the greatest improvements in the microscope as a working instrument was that carried out by Mr. Jackson in the construction of the continuous bar, supporting the body of the instrument above the stage, and carrying a small secondary body below, the whole bar being planed from end to end on one level, and with rack; this secondary body carrying the achromatic or other condenser, polarising prism, dark well, &c. In this way the axis of the instrument is per- fectly continuous, and no centering or adjustment is required. Three sets of castings were made from the patterns which he had constructed, two of which were given to his friends, Mr. Alfred White and the late Mr. Greening; and the patterns were then transferred to Messrs. Smith and Beck, and exist in the present form of their No. ] instrument. In 1858 Mr. Jackson was elected one of the managers of the London Institution. In his own profession in mechanical surgery he exhibited considerable tact and skill; and although such requirements were seldom brought into action, yet it was a source of great delight to him if he could by some simple contrivance alleviate the suffermgs of his patients, and thus facilitate their cure. One of the last undertakings of his life was the production of a very simple and most efficient contrivance for reducing dislocations of the shoulder-joint—an operation at times, in very muscular subjects, very difficult to perform. His quiet and unassuming manners, his clear and upright mind, rendered him generally beloved; and the readiness 33 | The President’s Address. with which he was ever willing to communicate to others whatever knowledge he might have acquired made his ac- quaintance and society both profitable and engaging to all who had the privilege of his friendship. The other gentlemen whose loss we regret were more distinguished for their love of science than for their practical investigations. The several reports which have been read to you will show that the Society is in a flourishing condition; its members, its list of books, and its museum are being daily increased ; and though your President has been unable to perform the duties of his office, -yet owing to the kindness of friends his place has been most ably filled, and in the hope that in years to come more and more will join our ranks, he begs to resign the chair to one who is in every way calculated to do it honour. OD _ Descriptions of New and Rare Diaroms. Series I. By R. K. Grevitie, LL.D., F.R.S.E., &e. (Read March 12th.) STICTODISCUS, N. gen., Grev. Frustues simple, discoid, divided by radiating lines into numerous plicate compartments. Lines not reaching the centre. Compartments furnished with conspicuous transparent, pore-like puncta. (In the four typical species, large scattered puncta also occupy the blank central portion of the disc.) This genus is founded primarily upon Discoplea ? Rota and D.? Rotula of Ehrenberg, and two most beautiful dia- toms which occur in a deposit found in the Island of Trinidad. While engaged in preparing a description of the two latter, my friend, Mr. Ralfs, directed my attention to the idea thrown out by Ehrenberg, that Actinoptychus dives, and Cyclotella Rota, and C. Rotula might be generically associ- ated ; and that they would come very conveniently into the new genus I was proposing to establish. The words of Ehrenberg are (under his definition of Discoplea ? Rota)— “© Proxime ad Actinopiychum divitem in Grecia fossilem acce- dens forma, et cum ea forsan, et cum sequente (Discopilea ? Rotula) in peculiari genere reponenda.” (‘ Bericht. Berl. Akad.,’ 1844, p. 202). I entirely concur in this view. Four of the species enumerated in this paper, namely, Séictodiscus Buryanus, S. Johnsonianus, S. Rota, and S. Rotula, may be considered typical, being distinguished not only by the pore-like puncta or papille, or whatever they may be called, which occupy a definite (?) arrangement within the compart- ments, but by large puncta remotely scattered over the con- vex and otherwise blank centre of the disc. The remaining species, which agree in general habit, and in the presence of definitely arranged puncta or cellules within the compart- ments, may be at least retained provisionally. For the discovery of the deposit in Trinidad, new, I believe, to the microscopic world, we are indebted to Dr. John Davy, well known for his researches in various departments of natural history. He kindly informs me that, from his obser- vations made in ‘Trinidad, he is disposed to consider the formation in which the deposit .occurs as connected with the New Red Sandstone ; adjoining to which is the sandstone, pro- bably of the same description, in which the Pitch Lake is 40 GREVILLE, on New Diatoms. situated. The extent of the deposit is not known; but, like that in Barbadoes, it is probably large both im surface and depth. It does not contain a great variety of diatomaceous forms; but various new and interesting species have already been observed in it. Stictodiscus Buryanus, n. sp., Grev.—Pore-like puncta at the marginal extremity of each compartment, forming a pyramidal group ; rays 30; diameter ‘0040" (Pl. IV, fig. 1). Hab. Deposit at South Naparima, Trinidad; Mrs. Bury. The disc of this superlatively beautiful diatom is trans- parent and gently convex, remotely dotted over with large, clear, pore-like puncta, exhibiting also the shadows of puncta belonging to the lower valve. The marginal groups consist of six orseven. The radiating lines (septa?) are free for more than half their length, and then, after anastomosing, become faint and inconspicuous before reaching the centre. When these lines are accurately focussed, the plicate character of the disc is not visible, but by changing the focus it becomes conspicuous (fig. 2). A. single specimen only has hitherto been observed, for which my cabinet is indebted to the generous kindness of its discoverer. Stictodiscus Rota (Khr.), Grev.—‘“ Disco amplo superficie | ineequaliter papillosa, papillis centralibus majoribus, margine radius 52 squalibus centrum non attingentibus intervallorum papillis sparsis.”’ Discoplea? Rota, Ehr., ‘Bericht. Berl. Akad.,’ 1844, p. 202; ‘Microgeol.,’ pl. xxxv, a. 22, fig. 6. Cyclotella Rota, Kutz., ‘Sp. Alg.,’ p. 19; Ralfs in Pritch, “tntfus.,’ 4th edit.--p-:, 812: Hab. Southern Ocean. The figure given of this diatom, by Ehrenberg, indicates very clearly that it is a genuine Stictodiscus. The valve is very large, the radiating lines much shorter than in the other species; the puncta within the compartments disposed, appa- rently, mm an irregular double series, and extend as far as the termination of the lines. The whole central space is covered with numerous large puncta, as in the preceding species. Stictodiscus Rotula (Ehr.), Grev.—Puncta equal, remotely scattered over the blank centre of the disc, those within the compartments irregularly (?) disposed ; rays 20. Discoplea? Rotula, Uhr., ‘ Microgeol.,’ pl. xxxv, a. 22, Tes Cyclotella Rotula, Kiitz., ‘Sp. Alg.,’ p. 19; Ralfsin Pritch. ‘ Infus.,’ 4th edit., p. 840. ie Hab. Southern Ocean. ate oe | became GREVILLE, on New Diatoms. 41 A very small species compared with the preceding, but evidently closely allied to it, the prominent character of the scattered central puncta being distinctly exhibited in Ehren- berg’s rude figure. The small number of rays at once separates it from all the others. Stictodiscus Johnsonianus, n. sp., Grev.—Pore-like puncta of each compartment equal, forming a short linear series; rays 50; diameter -0034”. (Pl. IV, fig. 3.) Hab. Deposit at South Naparima, Trinidad; Christopher Johnson, Esq. Not less beautiful than Stictodiscus Buryanus, and well distinguished by the single series of puncta in each compart- ment, which extends from the margin to about a third of the distance between it and the centre. Other puncta are scattered over the surface of the disc, as in the two previous species. A single example only has been found, for the possession of which I have again to acknowledge the kindness of Mrs. Bury. Stictodiscus insignis, n. sp., Grev.—Cellules large at the margin, forming a moniliform series in each compartment to near the centre; rays 46; diameter 0021”. (Pl. IV, fig. 4.) _ Hab. Barbadoes deposit ; very rare. A small but exquisite diatom, of which I have as yet only seen two individuals. It will be at once recognised by the puncta, or in this instance rather cellules, which, commencing at the margin, continue in a moniliform series, and de- creasing gradually in size until they approach the centre, when they lose their radiating character and occupy the entire surface. In this species we do not find the peculiar puncta scattered over the central portion of the disc, so characteristic of the three preceding species, while the centre itself is fully occu- pied with puncta or minute cellules similar to those of the compartments. ‘The valve is also much less convex. Stictodiscus dives (Khr.), Grev.—Pore-like puncta in each compartment minute, equal, forming a single series; rays 52 (centre minutely punctate 7). Discoplea? dives, Ehy. Actinoptychus dives, Ehr. ‘Microgeol,’ Pl. xix, fig. 12 ; Ralfs in Pritch. ‘ Infus.’ 4th ed., p. 840. Cyclotella dives, Kiitz., ‘Sp. Alg.,’ p. 20. Hab. gina. The appearance of this disc, as far as we can judge from Ehrenberg’s figure, is sufficiently striking to justify its pro- visional admission into the genus. No central punctation, however, is exhibited in the figure. VOL. I.—NEW SER. d 42 GREVILLE, 07 New Diatoms. CoscINODISCUS. Coscinodiscus armatus, n. sp., Grev.—Cellules minute, equal, radiating, about 13 in 001”; the disc furnished, towards the margin, with numerous, radiating, spine-like ridges. Diameter 0025” to -0035") « (PITV, fig.*5.) Hab. Barbadoes deposit ; very rare. A curious species, resembling very closely, in the marginal ridge-like spmes or processes, Brightwellia Johnsoni (Ralfs, MS.); one of the most beautiful of the many new diatoms which have been found in this deposit. When the disc is viewed in the position in which it usually presents itself, that is, vertically, these processes appear as short, thickened lines tapering towards the centre; but an oblique view brings out their real character. Coscinodiscus tuberculatus, n. sp., Grev.—Dise with a deep pore-like umbilicus; cellules radiating, subequal, the longer series terminating in marginal tubercles; cellules 9 in -001"; marginal striz 25 in ‘001’. Diameter :0025” to 0035”, or mor. (Fig. 6.) Hab. Barbadoes deposit ; frequent. Cellules hexagonal; those immediately surrounding the um- bilicus small; the rest nearly equal till near the margin, where they become again smaller. The longer rays of cellules appear to be in pairs, and it is the line of separation between them which terminates in the tubercle. The latter, on an oblique view, is seen to form an obtuse process. The margin is dis- tinctly and rather broadly striated. Coscinodiscus biradiatus, n. sp., Grev.—Granules distinct, fillmg up the centre irregularly, afterwards radiating, large, prominent, somewhat quadrangular, gradually diminishing in size to the margin; rays distant, the long ones alternating with a shorter series; margin with a row of minute puncta. Diameter :0035”. (Fig. 7.) Hab. Barbadoes deposit ; rare. An object of exceeding beauty and brilliancy. The disc is very convex; and in taking a vertical view, and in passing the focus down the side of the disc, the effect is very striking ; the prominence of the granules bemg so great as to cause the rays, when so viewed in perspective, to resemble the ribs and tubercles of a Cardium. There is no umbilicus. Coscinodiscus elegantulus, n. sp., Grev.i— Granules minute, subequal, irregularly scattered over a central space equal to about a third of the diameter of the disc; they afterwards form a single series of distant, often somewhat curved, rays ; margin with a row of very minute puncta. Diameter -0017”. (Pig. 2.) : (ZREVILLE, on New Diatoms. 43 Hab. Barbadoes deposit ; rare. A very delicate, transparent little disc, easily overlooked, but well marked by its wide fringe-lke rays. Coscinodiscus Barbadensis, n. sp., Grev.—Disc divided into compartments by double lines of punctiform cellules, the intervals between the lines being so clearly defined as to pre- sent the appearance of rays; cellules within the compart- ments less conspicuously radiate, subequal, except at the margin ; 15 in 001”; diameter of disc 0025". (Fig. 9.) Hab. Barbadoes deposit ; very rare. Disc convex, very delicate, and apt to be overlooked even by careful observers. Under a moderately magnifying power it would scarcely be taken for a Coscinodiscus, as it rather suggests the idea of an Actinocyclus (Ehrenberg, not Smith) ; but, under a higher power, the apparent rays are found to re- sult from the space left between two lines of cellules, which radiate from the centre to the circumference. Further ob- servations may determine the presence of an umbilical pore. One of my specimens is injured at that part; and the other shows, although obscurely, an approach to such a character. TRICERATIUM. Triceratium capitatum, n. sp., Ralfs.—Valve with the angles much produced and capitate, and separated from the centre by a transverse line; surface with indistinct, scattered puncta, and two spines. Distance between the angles about 0019”. (Fig. 10.) Hab. Barbadoes deposit ; extremely rare. « A small species, with very indistinct puncta. Valves, irrespective of the produced angles, straight or slightly con- vex.” (Ralfs.) The frustule appears to be not unfrequently imperfect or mutilated. I had examined half a dozen ex- amples before I perceived any trace of puncta at all. Mr. Rylands then kindly communicated a specimen, in which, in addition to the central puncta, a few larger and more definite puncta were scattered on the narrow portion of the produced angles, and the surface was also furnished with two conspi- cuous spines. I have subsequently found two frustules myself, exhibiting very distinctly these characters. Triceratium Westianum, n. sp., Grev.—Sides of the valve deeply and sharply concave; angles forming segments of circles, separated from the centre by transverse lines ; margin of the angles with very short radiating lines ; surface strongly punctate; distance between the angles 0018." (Fig. 11.) Hab. Barbadoes deposit ; extremely rare. | A4 GREVILLE, on New Diatoms. I have much pleasure in dedicating this remarkable and ornate species to my friend, Mr. Tuffen West, the unrivalled illustrator of the Diatomacez, and who is well acquainted with the nature of the objects themselves. It. is allied to Triceraiium castellatum, described by himself, from the same deposit, m the eighth volume of the ‘ Transactions of the Microscopical Society ;? but is, in several important cha- racters, perfectly distinct. Like most of the species of Tri- ceratia discovered in this mine of novelties, it is excessively rare. I have only met with six specimens. Triceratium Barbadense, n. sp., Grev.—Sides of the frustule gently concave; angles broadly rounded, separated from the centre by transverse lines; whole valve closely and minutely punctate. Distance between the angles 0016”. (Fig. 12.) Hab. Barbadoes deposit ; excessively rare. Allied to 7. castellatum, but differs in the form; the sides of the valve not being nearly so deeply concave, and the angles, instead of swelling into segments of circles, being merely broadly rounded. Triceratium nitidum, n. sp., Grev.— Sides of frustule rather deeply concave, angles ovate, separated from the centre by transverse lines; whole valve punctate; puncta of the central space radiating, and becoming conspicuous as they reach the margin. Distance between the angles, 0014”. (Fig. 13.) Hab. Barbadoes deposit ; extremely rare. I am not aware of any described species for which this can be mistaken. A good character exists in the puncta of the centre, which radiate in single lines, becoming gradually larger and the lines more distinct as they approach the margin. Triceratium cellulosum, n. sp., Grev.—Sides of the valve straight ; angles with pseudo-nodules, obtuse, separated from the centre by transverse lies; centre and angles coarsely and irregularly cellulose; cellules of the former more or less ovate or oval, and disposed in a radiating direction, though not in lines ; those of the latter in rows parallel with the sepa- rating line. Distance between the angles 0026”. (Fig. 14.) Hab. Barbadoes deposit; exceedingly rare. Large and robust, as compared with many of the Barbadoes species; and so peculiar in its characters as to be instanta- neously recognised. ‘The cellules of the angles are somewhat quadrate, and hence those parts of the valve have a sort of cancellated aspect. The lines which separate the angles | from the central area appear as linear spaces left unoccu- pied by the cellules. Murrayfield, Edinburgh ; January 15th, 1861. GREVILLE, on New Diatoms. 45 The following new species of Zriceratium have also been discovered in the Barbadoes deposit, and will be figured and more fully described in a future number. T. aculeatum, Grev.—Sides of valve gently and evenly concave; angles somewhat obtuse, with a decided pseudo- nodule; granules irregularly radiant; centre convex, with three spines. Distance between the angles -0022". T. cornutum, Grev.—Valve (in my specimen four-angled) with straight sides, and sharp angles furnished with strong horn-like processes ; surface minutely granulose in radiating lines; centre with three spines. Distance between the angles ‘0015”. T. productum, Grev.—Valve punctate; angles produced, capitate; centre divided imto compartments by radiating, vein-like lines. Distance between the angles :0027”. T. inconspicuum, Grev.— Minute, sparsely punctate ; valves (in my specimens four-angled) with the angles semicircular, separated from the centre by a transverse line; centre bordered with a row of puncta. Distance between the angles ‘0005’. T. delicatum, Grev.—Minute ; valve with shghtly concave sides and broadly rounded angles, filled up with transverse rows of fine puncta; centre containing a pale, obtusely tri- angular band, within which is a triangular spot bordered with puncta. Distance between the angles 0012”. T. ornatum, Grev.—Valve with rounded angles and convex sides ; conspicuous pearly granules sparingly scattered in the semi-blank central.space, and forming a broad marginal band of radiating lines, which are 7 in ‘001’. Distance between the angles 0024”. LT. labyrintheum, Grev.—Valve with rounded angles and slightly convex sides ; the centre occupied with a network of widely anastomosing, vein-like lines, from the boundary of which short lines are given off towards the margin; spaces enclosed by the anastomosing lines finely punctate. Distance between the angles -0023”. T. blanditum, Grev.— Sides of valve (in my specimen four-angled) deeply concave; angles sub-hemispherical ; centre with a small blank space; granules conspicuous, sub- remote, equal, forming straight, equidistant, parallel lines, 11 in 001". Distance between the angles ‘0020". » pee Shel, ee ae TRANSACTIONS. On the MeramorpHosss of a Coccus found upon ORANGES.* By Ricuarp Brcx. (Read March 13th, 1861.) Ir the external surface of almost any of the sweet oranges be only cursorily examined, it will be found more or less spotted with small scales, the shields of a coccus or scale insect ; they are adherent to the rind of the orange, but can easily be detached; and, on turning one of the larger ones over, it will be found, on examination under a low power, to present, as the most striking feature, a large accumula- tion of eggs lying beneath a cottony secretion (Plate V, fig. 1, 6); very frequently these eggs are in the process of hatching, and, under such circumstances, we have the insect in its larva state (fig. 3). The body is white, oval, and very flat: there are two antenne proceeding from underneath; they are about one fourth the length of the body, rather hairy, and of eight or nine joints, two very small light-pink ocelli, or simple eyes, occur one on each side, at the very edge of the body, and about where the long curves of the oval commence ; consider- ably below the antennee is a proboscis, a long and apparently horny tube, proceeding from a conical base. These, with the exception of a few isolated hairs, are the only external organs of the head that are apparent. The legs are six in number, each consisting of, I think, four members; the terminal ones being provided with a hook, and two or more very small suckers hardly to be distinguished from * The author considers these observations as very incomplete; his object in laying them before the society in such a state was to afford any member an opportunity of investigating the subject whilst the oranges were in season, having since found that the same coccus is in great quantities on plants in this country, and that the eggs are now hatching; he would still call the attention of microscopists to the subject. | VOL. I.—-NEW SER. é 48 Beck, on the Metamorphosis of a Coccus. hairs. At the extremity of the body two exceedingly minute hairs trail behind for some considerable length ; and besides these are numerous setz and orifices, parts, I believe, of the organ for the secretion of the cottony substance and the hard shield. The locomotive power of the larva—and this is the only time it makes use of it—is I believe very limited; frequently it settles close to the parent home, and Ii imagine that when once the proboscis is inserted in the orange it is never removed; the insect thus located, the skin on the back changes to a darker colour, thickens, and ultimately becomes a cast skin, the coccus having retreated between the secretions of the hard shield, as a protection above, and the cottony substance as a close attachment below, but to neither of them is it ever adherent; at this stage it also loses every trace of antenne, legs, and eyes, whilst, on the contrary, the proboscis is more fully developed : this is evidently the pupa state, and thus far I have been unable to detect any difference between male and female. The first indication that I have found of the male insect is the presence of two dark and rather diffused red spots in the head, and also a simultaneous disappearance of the proboscis (fig. 4). Then after a skin is cast, there is an entire disappearance of the organs for the secretions of the shield, which is completed of a long and narrow shape; one stage more in advance and the ocelli are black and distinct, and there can be traced two long antennz and two wings at the. side; six legs are also in process of development, the two in front being directed forward, which is a peculiarity of the pupa of this genus; and at the extremity of the body is a protuberance I imagine to be the male organ (fig. 5). Another skin is yet cast, and then there is a perfect male insect (fig. 6). The ocelli are four, two above and two below; the antenne, eight or nine jointed, very delicate, hairy, ‘and nearly the length of the whole body ; the legs have four members, the terminal one of each being provided with a single hagk and two or more delicate suckers; the wings project considerably beyond the body, they are transparent, but covered with very minute hairs, and strengthened by a simple ribbing of two corrugations which unite at the base. ‘The two halterers or poisers are oval, and terminate with a hair bent like a hook at the extremity; and that which I presume to be the male organ is long, attenuated, and attached at its base to; and immediately above, a truncated projection which has an aperture at its apex. ~ We thus find in the male complete insect metamorphoses. Beck, on the Metamorphosis of a Coccus. 49 I am unable to say as much of the female, though I presume such must be the case, as only a perfect insect is capable of reproducing its species. I have not as yet paid as much attention to this sex, but so far as my investigations have gone, after it has changed into the pupa state all external organs entirely disappear, excepting those at the extremity of the body, and the proboscis, which becomes stronger and larger (fig. 8) ; the secretion of the shield is continued until nearly four or five times the size of the male, and the body of the insect bears about the same proportion; it then deposits ‘ts eggs, between one and two hundred in number, which are placed on end in great regularity, and the first ones will frequently be found hatching before the last are laid. The external surface of the shield of the male (fig. 7) gives very marked indications of the three changes that have taken place: first, there is the cast skin of the larva; secondly, the shield for the pupa; and thirdly, a thin and short addition to the shield for the wings of the imago, which I believe is lifted up when the insect escapes. There are also three similar indications on the external surface of the female shield, and these may also warrant the conclusion that its metamorphoses have been complete. It is somewhat surprising that these cocci are to be found im a living state at all, after the change they must have ex- perienced in the climate ; it is, however, very evident that the larva and pupa states are much hardier than that of the Imago; at least so far as the males are concerned, I have found it very difficult to obtain any alive after the external organs were fully developed. As itis, the circumstances under which they appear are very favorable to their examination; one single orange, if well selected, will supply every condition I have mentioned ; and I imagine that from the fact of the shield being such a complete protection, the metamorphoses are more distinct in their development than under the more ordinary circumstances where the insect itself is exposed. I have invariably used Mr. Wenham’s binocular arrangement with the microscope, and I can only say that for this class of investigations the results are perfectly marvellous. 50 On the Microscopic CHaRAcTERS of the Crystats of ARSENI- ous Acip. By Wiuiiam A. Guy, M.B. Cantab., Pro- fessor of Forensic Medicine, King’s College, London. (Read May 8th, 1861.) In submitting to your society this paper on the miscro- scopic characters of the crystals of arsenious acid, I have two principal objects in view. I wish, in the first place, to illustrate, by a striking instance, the great value of the binocular microscope as a means of diagnosis; and, in the second place, to give a more exact account than any at present in existence of the crystalline forms assumed by a very important poison. That to render such an account is not a work of mere supererogation, a reference to the descriptions of the crystals given in works of authority would readily prove. : Most authors describe the crystals as regular octahedra, without recognising any other crystalline forms. Some writers, however, speak of the regular octahedron and its modifications, or of forms traceable to the octahedron; and acicular crystals, long prismatic needles, triangular and hexagonal plates, and even tetrahedra, are to be met with in the descriptions of authors.* I may add that, in illustrated works, the octahedral crystals are usually figured in the form in which they are most readily identified ; the less usual positions of the octa- hedra and the rarer forms and modifications of the crystal being omitted. The imperfect and somewhat conflicting accounts thys given of the crystals of arsenious acid are, doubtless, to be explained, partly by the difficulty of examining them, whether by lens or microscope, when sublimed, as they were for- merly, in thick reduction-tubes of narrow bore; partly to the great variety of lights and shadows presented by the crystals, especially when viewed by transmitted light; and partly to the imperfect relief given to the crystals when examined by the monocular microscope. * Consult Pereira’s ‘Materia Medica,’ 4th edition, p. 685, in which the tetrahedron is mentioned as one form of the crystal; Miller’s ‘ Elements of Chemistry,’ part ii, p. 961, in which mention is made of long prismatic needles, isomorphous with those of oxide of antimony; and Taylor, on ‘Poisons,’ 2d edition, p. 385, in which equilateral triangular plates are specified. Pereira cites a foreign authority (Wéhler) who found in a cobalt roasting-furnace arsenious acid crystallised in hexahedral plates derived from a right rhombic prism. Guy, on Crystals of Arsenious Acid. 54 The substitution of the modern form of reduction-tube, in which the vapours of arsenious acid are made to pass through a narrow glass tube with thin sides, has made the examination by the microscope more easy; but the simple plan which I suggested about three years since, for obtaining the crystals on a flat surface, has offered still greater facilities, of which it is but natural that I should have largely availed myself. The knowledge of the subject thus obtained may be said to have been completed by the use of the binocular micro- scope. The most superficial and cursory examination of the first specimens obtained upon a flat surface sufficed to con- vince me that very much remained to be done before our knowledge of the true crystalline characters of arsenious acid could be placed on a level with the practical importance of such knowledge. In the first place, it was quite clear that those descriptions which spoke only of the regular octahedron as the one proper form of the crystal were wholly inade- quate; and that even those which recognised, not only the perfect crystal, but all the forms traceable to the octa- hedron were still insufficient. We ought to know what particular forms to look for. Again, it must be interesting, and might be practically important to know something more of the alleged acicular or prismatic crystals, of the triangular and hexagonal plates, and of the tetrahedra, described and figured in Pereira’s work. The crystallographer, too, could scarcely abstain from speculating on the possible occurrence among these octahedra of those other members of the re- gular system, the cube and the rhombic dodecahedron. Some, if not all, of these questions I hope to be able to answer, without proving tedious to those who have not the special interest in this subject which I have myself. Re- verting to my early examinations of the crystalline deposits of arsenious acid as obtained on a flat surface, I may state that I encountered many forms and ‘appearances which I was not able to explain to my own satisfaction. When viewed by transmitted light, a large proportion of the crystals wore the appearance of dark squares, a smaller number of dark oblong figures, a still smaller number of long, thick, black lines. These latter, the long lines, I took to be the acicular or prismatic crystals described in books. The dark squares and oblongs were not so readily explained. Then, again, I encountered among the crystals transmitting or reflecting light, in addition to forms which might be merely different attitudes or postures of the regular octahe- dron, or of the truncated octahedron, or of the lengthened 52 Guy, on Crystals of Arsenious Acid. octahedron, well-formed triangular prisms, terminated at either end by triangular facettes, also twin-crystals or mdcles, also equilateral triangles resting on half the adjoming triangle as a base. I will not take up your time further by specifying all the forms which at first puzzled and perplexed me. Suffice it to say that, in the full consciousness that I did not understand the things I saw, I determined to turn for awhile from nature on the small scale to art on the large. I procured octahedra of wood, and not being satisfied with them, prevailed on Messrs. Powell, of Whitefriars, to make me the crystals of glass now before you. By studying these large models, placing them in all sorts of positions, and viewing them from different points and in different lights, I was pre- pared to understand most of the appearances under the microscope. The broader shadows of the transparent glass crystals were reproduced in the small crystals of arsenious acid, and the several postures which I caused the large crystals to assume were recognisable under the microscope. I found that the sublimed crystals adhered to the flat surface of glass by their solid angles, by their edges, and by their faces, as well as in positions less easily described. I also inferred that the dark squares were crystals (octahedra) adhering to the glass by their solid angles, in which position, as my glass model taught me, the play of lights and shadows was such as to occasion confusion and possible darkness. This suspicion, which was strengthened somewhat when I examined the sublimates by reflected light, became certainty under the binocular microscope. Under that admirable mstrument, with refleeted light, there are no dark masses, and no obscure forms. The meaning of the dark oblong forms and of the dark lines which I at first identified with the acicular or prismatic crystals of authors did not occur to me till later in my inquiries. I have mentioned the frequent occurrence of the three-sided prism with bevelled extremities. I do not mean the figure sometimes described as a lengthened octahedron, but a figure having the deceptive appearance of a triangular prism. Was this a distinct crystalline form, or might it not be some aspect of the octahedron? It obviously could not be brought about by any attitude of the whole crystal; but my wooden model, supplied by Professor Tennant, is cut in half by a plane parallel to, and equidistant from, two of its faces, and these two equal halves of the-crystal are made to rotate on each other, so as to show the twin-crystal, or mécle. Here, then, without supposing any new form of crystal, there was new material for speculation. I had seen the twin-crystal, or mdcle, m Guy, on Crystals of Arsenious Acid. 53 almost every specimen I examined. Hence, it was clear that half-crystals were among the possibilities of arsenious acid sublimed. Well, this half-crystal which I was soon en- couraged to have made in glass, when placed in a certain position, gave me the precise figure which had perplexed me ; it gave also the equilateral triangle with the half adjoming triangle for its base (one of the commonest crystalline forms) ; also, the half-triangle itself; also the hexagon, and the hexagon tipped with three small, dark, triangular facettes. Now this appearance of a triangular prism, terminated at each end with an equilateral triangle, is given by the tilting forward of the half-crystal; and just as the whole crystal adhering by a solid angle becomes by transmitted light a dark square, so this half-crystal appears as a dark oblong. _ But the long dark lines which I had taken for needles or prisms, what were they? Possibly not distinct and separate erystals, but only deceptive appearances like the dark squares and oblongs. Could they be the forward edges of large deep plates, owing their dark appearance to the same depth of erystalline mass? It was reserved for the binocular microscope to demonstrate this. On examining with this instrument a vast number of specimens, and passing under review thousands and thousands of crystals, I find many large hexagonal plates with their edges thrown forward, but very few prismatic erystals. I also find triangular plates of various thickness, square plates also of varying stibstance, and a few rhombic and rhomboidal plates. But my catalogue is not yet exhausted. Before I made use of the binocular microscope, I thought that I had encountered one or two cubes; but as the assertion that I had met with cubes was received somewhat incredulously, I looked for them in the field of the bmocular with great interest. I found several figures which approachéd very closely to the cube, and in one instance encoutitered a perfect cubical crystal. I say this without any sort of hesitation. I have also more frequently met with the rhombic dodecahedron, and its mdcle, or twin-crystal. I have not yet seen a tetra- hedron; though in one specimen obtained from Scheele’s green, and abounding in triangles less symmetrically formed than usual, I thought that I discerned the marks of the tetrahedron. Be thisas it may, I am quite sure that this form of crystal should be set down among mere possibilities : I have not seen it in any one of many hundreds of specimens of crystalline deposit ob- tamed from arsenious acid itself, or from the metal arsenic. It is probable that the deep triangular plates, which abound In some specimens, have been taken for tetrahedra. I have now briefly sketched the course of experiments, ob- aa ¢ 4 Guy, on Crystals of Arsenious Acid. servations, and inferences by which I was gradually possessed of my existing knowledge of these interesting crystalline forms. Something I learnt from actual examination; such, for in- stance, as the common appearances of the perfect octahedron, and the fact of the existence of plates of various forms, as well as of crystals other than the octahedron. Something more I learnt byinferences drawn from the close examination of models of the crystal and half-crystal, opaque and transparent. I understood at once the twin-crystal, or mécle. J inferred that the equilateral triangle mounted on a half-triangle as its base, the hexagon with three-shaded points, and the triangular prism were merely phases of the half-crystal; and I thought it likely that some of the detached equilateral triangles and some of the hexagons might be explained in the same manner. But I remained quite satisfied with the belief that a con- siderable number of the long narrow crystals were prisms. I was not quite satisfied of the existence of triangular plates or of hexagonal plates. I spoke doubtfully about cubes, and had not been able to make out the rhombic dodecahedron ; and I felt that my views concerning the large part played by the half-crystal, though highly probable, were still only pro- bable. But under the binocular microscope all my doubts were dissipated, all my errors corrected, some surmises con- firmed, and most of my inferences justified. That which had been a work partly of observation, and partly of reasoning, be- came a simple matter of sensation. If there is any one who doubts the value of this form of the microscope, or 1s disposed to treat it simply as a philosophical toy, I will ask him to ex- amine these crystals with the monocular microscope by trans- mitted light, and with the binocular microscope by reflected light; and I would especially commend to his attention the crystalline and globular sublimate (crystals of arsenious acid, and globules of metallic arsenic) shown in the capillary reduc- tion-tube. The fine relief and perfect roundness of the tube and its contents is, at one and the same time, a proof of the utility and of the faithfulness of the binocular microscope. With a view to give completeness to this paper, I will first briefly describe and illustrate by appropriate engravings, corresponding with the large diagrams and models shown at the meeting, the various attitudes and appearances of the entire octahedron and of the half-crystal, as deduced from the study of models of wood and glass,* and then exhibit some * Since the paper was read, I have added studies of the rhombic dode- cahedron, similar to those of the octahedron which were shown in the diagrams exhibited at the meeting. This addition goes far towards ex- hausting the crystalline forms of sublimed arsenious acid. On Guy, on Crystals of Arsentous Acid. 5, uf the leading forms as seen under the monocular microscope by transmitted hight, and under the binocular microscope by reflected light. I also append, at the desire of the editors of the Journal, a short account of the best mode of obtain- ing the crystals of arsenious acid for microscopic examination. 1. The entire crystal. Q . The crystal adhering by one of its edges, and displaying two sides (fig. 1). 6. The crystal adhering by one of its faces, and displaying three sides (fig. 2). Sy The crystal adhering by one of its faces, and so seen as to display four sides (fig. 3). d. The crystal adhering by a solid angle, so as to show four equal faces (fig. 4). In this position the crystals appear by transmitted light as black squares. % The crystal adhering by one of its faces, and showing the lights and shadows of the transparent model (fig. 5). 2. The half-crystal. The regular octahedron may be divided into _ two symmetrical bodies— 1. By a plane parallel to two faces of the crys- tal (fig. 6). The sections thus formed are bounded by a hexagon and by an equilateral triangle, and they have the appearance shown in He.) 7; 2. By a plane passing through four edges of the crystal, each section being a four-side pyramid on a square base (fig. 8). 3. By a plane cutting the equilateral triangular faces of the crystal into two equal right- angled triangles, each section presenting a rhombic face (fig. 9). 56 Guy, on Crystals of Arsenious Acid. The first section supplies the following forms : : a. The equilateral triangle (fig. 10). 6. The equilateral triangle resting on half the adjoiming triangle as a base (fig. 11). This is a very common aspect of the half-crystal. c. The hexagon. (fig. 12.) d. The hexagon with the three small triangular facettes in shadow (fig. 13). This also is a very common aspect of the half-crystal. e. The half-triangle (fig. 14.) f. The edge of the half-crystal tilted forward, so as to give the appearance of a triangular prism (fig. 15). This again is a very common aspect of the half-crystal. g. The mdcle or twin-crystal, formed by the partial rotation of two half- _ crystals on each other (fig. 16). h. The same, with the triangular face of one half-crystal visible (fig. 17). The second and third sections are of rare occurrence, and do not assume appearances requiring more minute description. 3. The rhombic dodecahedron. a. Three sides visible, so as to resemble the perspective of a cube (fig. 18). 6. Four sides visible, and a solid angle pro- jected forward (fig. 19). c. Five sides visible (fig. 20). d. Five sides visible; another aspect of the crystal (fig. 21). Guy, on Crystals of Arsenious Acid. ae e. Six sides visible (fig. 22). jf. The médcle or twin-crystal of the rhombic dodecahedron (fig. 23). g. The méecle or twin-crystal; another view (fig. 24). Having now figured some of the leading « Appearances eich the models of the octahedron and rhombic dodecahedron, with their half-crystals, may be made to assume by changes of position, I proceed to give a brief summary of the crystalline forms which I have been able to distinctly recognise in the course of my examinations of the sublimates of arsenious acid. i rhe crystalline sublimates of arsenious acid consist of regular octahedra, rhombic dodecahedra, cubes, plates, and prisms. 2. The regular octahedra may be entire and homogeneous, or they may be variously truncated and notched, mottled and figured ; and they may assume any of the forms depicted in figures 1, 2, 3, 4, and 5. 3. The entire vegular octahedron may ies be modified as in the annexed engraving (fig. 25). 4. The octahedron may present itself as a half- crystal in any of the forms depicted in figures 7 to 15, inclusive. 5. The half-crystals may be combined to form mdcles, or twin-crystals, as in figures 16 and 17. 6. The entire crystal and the half-crystal may have their edges notched, so as to yield figures 26 resembling the trefoil, or fleur-de-lis, as in the Noe annexed figure (fig. 26). 7. The rhombic dodecahedron may present itself entire in any of the forms depicted in figures 18 to 22. 8. The rhombic dodecahedron may present itself as a half- crystal; and two half-crystals may be united to produce the mdcles, or twin-crystals depicted in figures 23 and 24. 9. The cube is a very rare form among the crystals of arsenious acid. 10. The plates present themselves as hexagons, equilateral triangles, squares, rhombs, and rhomboids; and they may be of any thickness, from that of thin iridescent films, to the 58 Guy, on Crysials of Arsenious Acid. third or the half of the diameters of the faces of the plates. They may also greatly exceed in size the largest crystals of 59 _ the groups in which they are found. The principal a0 Vax ed » 0 i/ Je forms are shown in the annexed figure (fig. 27). 28 11. Sometimes compound plates of large size and symmetrical form are found united at angles corresponding with those of the faces of the octahedron, as in fig. 28. At other times they are grouped with great irregularity. In other instances plates, such as the equi- lateral triangle, are found built up by a hexa- gonal plate symmetrically jomed to three equi- lateral triangles, as in fig. 29. 12. The prisms are either four-sided prisms of small size, or they are large four-sided rectangular prisms terminated by four-sided pyramids (fig. 30). 13. Sometimes the prisms are shorter, and present the form depicted in the subjoined figure (fig. 31). To this detailed description it is only necessary to add that there is great variety to be found in groups of crystals of arsenious acid produced at the same time and in the same way. In some groups the crystals are perfect, free from spot or blemish, transparent, and brilliant; in others, notched or truncated, mottled and figured, and translucent; in some the regular octahedron is the prevailing form, other forms be- ing exceptional ; in others, plates predominte, and are nearly as numerous as the crystals themselves ; occasionally equilateral triangular plates occupy the whole field, to the exclusion of almost all other forms. The lithographic plate (Pl. VI) ap- pended to the paper, and showing the sublimates as they appear by the monocular and binocular microscope, by transmitted and reflected light, will give some idea of the variety of forms which the crystals assume. The best mode of obtaining the crystals of arsenious acid may be described in a few words. The apparatus required consists of a spirit-lamp with small flame, specimen tubes of small diameter and not exceeding an inch in length, and slides or discs of crown glass. A few grains of arsenious acid are placed in a clean and dry specimen tube, and this in a con- venient holder, consisting of a slip of copper or brass punched or drilled to receive it. The tube is to be held over the flame of the lamp till the acid collects as crystals, or as a white powder, Reape, on a New Hemispherical Condenser. 59 round the orifice of the tube. The slides or discs are then to be heated in the flame of the lamp, so as to drive off the moisture, and raise considerably the temperature, of the glass. The slide or disc, thus heated, is to be placed over the mouth of the tube, and kept there till bright spots appear on its under surface. The spirit-lamp is then to be removed, and the glass allowed to cool. The process may be conducted with the two hands over the lamp, or the holder may be supported on a retort- stand, as is shown in figure 32, and the spirit-lamp removed for a time after each operation. Good results can only be obtained when the slide or disc is heated ; but if too much heat is used, the crys- tals are dissipated as soon as formed. When the operation is quite successful, we obtain one of the most beautiful of microscopic objects, and one of the very : = best illustrations of the value of the binocular microscope as a means of identification and diagnosis.* On a New HemispHerican ConprnserR for the Microscope, and its use in illustrating an iwnportant principle in Microscopic Illumination. By the Rev. J. B. Reaps, PRA: (Read May 8th, 1861.) Tue condenser which I am now using has been so favor- ably received by several of my friends, that I am induced, at their request, to offer a description of it to the members of our society. I need scarcely say, that an unpretending single lens cannot be proposed as a rival to the almost per- fect combinations in use among us; but it may, perhaps, take its place as an efficient adjunct to the microscopes of those observers who are disinclined, from one consideration or another, to procure more expensive apparatus. The condenser consists of a hemisphere of glass, about one and three-quarter inches in diameter, with an arrange- ment of stops by which difficult test objects are well defined under half-inch object-glasses of 90° aperture. It is set in a thin brass ring, and screws upon a cylinder adapted, like other fittings, to the opening of the sub-stage of the microscope. * For a more detailed description of the mode of obtaining crystals of arsenious acid, consult a paper in ‘ Beale’s Archives,’ No. 111, 1858, and the ‘second edition of my ‘Principles of Forensic Medicine,’ in which several of the forms depicted here will be found figured. 60 READE, on a New Hemispherical Condenser. The hemisphere in question has been many years in my possession, though I did not apply it to the table micro- scope until February, 1860. It happened to be one of the lenses which Mr. Chamberlain, the optician, called “a sporting lot; and I may say, that on more than one occasion I have successfully used it in following optical game. In the year 1837 it did me good service when con- nected with the condensing lens of a solar microscope, inas- much as it gave me great light with little or no heat, and thereby prevented all risk in the use of achromatic object- glasses and objects mounted in balsam. The arrangement for this purpose is as follows:—A beam of solar light, containing both colorific and calorific rays, was transmitted through the condensing lens of the imstrument ; and, owing to the different refrangibility of these com- ponents of the beam, we have a cone of light-giving rays formed within a cone of heat-giving rays, and the principal focus of heat is further from the lens than the principal focus of light. But when these rays cross the axis, the cone of heat-giving rays lies within the cone of light-giving rays; and, if the hemispherical lens be placed in these second cones, at the distance of its own focal length from the principal focus of heat, it will be at a greater distance than its focal length from the principal focus of light; and, conse- quently, the rays of heat will be rendered parallel, while the rays of light will converge to a second focus, exhibiting great intensity of illumination, but without any sensible heat. I have approximately measured the heating power of the calorific rays in the second cone, when rendered parallel by the hemispherical lens; and I found, inthe month of December, that the mercury in a sensitive thermometer, when placed in the second focus, did not reach 90° Fah., while, at the same time, the heat in the focus of the first cone was sufficient to discharge gunpowder. The admirable drawing, by Lens Aldous, of the magnified head of a flea mounted in balsam, from which his well-known lithograph was made, is a good illustration of the practical value of this application of the lens; and it is probable that a cemented achromatic object-glass was then, for the first time, used with safety in the solar microscope. I also used the hemisphere, with a central disc of tinfoil upon its plain surface, as a means of obtaining a black- ground illumination in the solar microscope; and nothing can exceed the beauty of the brilliant tint of the Volvor globator and Hydra viridis under this arrangement. I found it impossible, however, to take a photograph of these objects Reape, on a New Hemispherical Condenser. 61 under this illumination, though with direct solar light I had no difficulty whatever. It is probable that a similar application of the hemisphe- rical Jens and central stop to the oxyhydrogen microscope, which our variable climate almost compels us to use, would in like manner throw into the pictures on the screen the additional charm of natural colours, and thereby greatly en- hance the interest of the exhibition. Notwithstanding my use of the condenser in the experi- ments just described, it did not occur to me to extend the application of it, until I was, as it were, driven by necessity. My old parishioners and other kind friends pre- sented me with a valuable microscope at the commencement of last year; and not having, in the first instance, any of the well-known condensers at hand, I used the light of two lamps placed at right angles to each other, and by means of suitable lenses I threw sufficient light on the rectangular markings of the P. acuminatum and other similar tests. I was much pleased with the effect of this simple method of illumination; and I am glad to find that Mr. Tomkins has also used it, but with considerable improvement, by employ- ing two achromatic prisms, which give brilliant Ulumination, while the “ marking shadows” are in deep relief. In order to obtain any proper definition of the markings, I found it necessary so to’ turn the valve of the diatom, that a line of markings might le at right angles to a line of light. In fact, in any other position the markings are scarcely visible ; and the conclusion seemed forced upon me, that the ordinary spot lens contains in its circle of hght a large portion of unnecessary, if not injurious, ilumination. With this impression on my mind, it suddenly occurred to me, that my old friend, “‘the kettle-drum,” as Mr. Gravatt calls my condenser, might play an important part, if its plain surface were coyered with tinfoil suitably pierced at the circum- ference for the tranmission of two pencils of light at right angles to each other. I made the experiment, and happily I can fall back upon the testimony of well-qualified ob- servers as to the success which attended it. The direct illu- mination of only one lamp was now sufficient, and, instead of rotating the object—always a difficult process in the absence of suitable adjustments—it was easier to rotate the secondary stage which held the condenser, and so gain the proper position of the two points of light. It may be well to state, that by taking out the eye-piece, and looking at the points of light down the body of the tube, we may at once, by the rotation of the sub-stage, place them in the right posi- 62 Reave, on a New Hemispherical Condenser. tion for illuminating any rectangularly marked valve whose position on the stage of the microscope is known. One point of light must le over the end of the valve for bringing out the horizontal lines; the other will be opposite the side of the valve, and will act on the longitudinal lines; and resolution into dots or squares will be immediately effected by adjusting the distance of the condenser. For oblique or diagonal markings, the apertures at the cir- cumference of the diaphragm must no longer be placed at 90° apart, but at such an angle as is indicated by the markings themselves. In the case of the P. angulatum, where there are three lines of markings, there must be three apertures, since with two apertures only, we should exhibit, according to their position, any two, and but two, of these three lines, in turn, and, at the same time, give a sort of unnatural elongation to the peculiar markings on the valve. The size of the apertures is 24° at the circumference and opposite side, and =i;ths of an inch in the direction of the radius. The latter dimension must be less in diaphragms for smaller hemispheres, and must never exceed half the radius of the condenser. In order to secure the best effect, the distance between the apertures must be adjusted with considerable accuracy. For this purpose I use a diaphragm of thin brass, or of strong tinfoil, having one aperture only, and by its rotation under a given valve of the P. angulatum, for instance, I bring into view the three lines of markings in succession, first the horizontal lines, and then the oblique lines, by rotating the diaphragm to the right and left, and thus the three points at which the apertures are to be made can be deter- mined with the utmost precision. If the aperture for the horizontal lines be made at the distance of 180° from the place thus obtained, these lines will be illuminated on their opposite sides, and the three apertures will be 120° apart, as in the diaphragm first cut out for me by Mr. Waterhouse, who happened to be working with me at the time. But in practice I find it not only better, but mdispensable, to illuminate all the markings on the same side, as by the first method, and preserve thereby that uniform direction of the shadows which is the key to accurate definition. A set of diaphragms thus obtained, and a diaphragm with a minute circular aperture in the centre only, for the central adjustment of the lens, complete the furniture of the condenser; and a brass ring sliding outside the top of the cylinder on which the condenser is screwed conveniently holds the diaphragms in their place, and admits of their being readily changed. Reape, on a New Hemispherical Condenser. 63 In the application of this condenser to the resolution of lined test objects, it will be seen that the principle sought to be carried out is to throw the axis of the pencil of illumi- nating rays in a direction at right angles to the line'to be: resolved. In all cases where the precise position of such lines is known, a supplementary diaphragm may be cut with the apertures in their correct mutual positions ;. but as these: position angles greatly vary in different diatoms on the same: slide, my friend, Mr. Waterhouse, ingeniously suggests the ‘use of a pair of similar diaphragms overlying each other, and capable of revolution round a common centre. For this purpose the diaphragm next the condenser must be fixed in position, and moveable with the lens, by means of the pinion motion of the sub-stage, while the other is attached to a deep hoop fitted upon the brass tube carrying the lens, so as to be conveniently rotated by the finger and thumb, applied to a. narrow milled ring, but sufficiently small to pass through the opening of the second stage, when the condenser is required to be removed for other purposes. To carry out this sug- gestion, place two diaphragms together, and mark out on. their circumference the positions of six adjacent apertures ;- cut out one aperture, pass over two, and cut out the remaining three; then turn them face to face, so that the small stops. between the apertures may coincide, and, by the rotation of. one diaphragm upon the other, the stop between two aper- tures, or little prisms, as they virtually are, may be made to. vary from about 30° to 120°. This will be ample scope for all bilinear, oblique, and rectangular markings. This method of arrangement also admits of the introduction of a third aperture for the P. angulatum, &c., and the whole diaphragm system is thus brought within the least possible compass. 3 The lens in its present form is simple, cheap, and easy of adjustment, though of course not free from chromatic aber- ration ; but the proper adjustment of the apertures to the object examined seems to prevent this error from being very apparent, and a pierced diaphragm beneath as well as upon the condenser has advantages in this direction, as well as. occasionally in others. The central pencil of about - goth of an inch in diameter, which gains intensity from the con- struction, is itself virtually achromatic, and is also very. effective for direct central illumination where obliquity is not required, or would be injurious. , - The angle of aperture of the lens is necessarily small; and therefore TI cannot help thinking, with Mr. Tomkins, that if: it,-were “possible - by: the..application of rotating pierced VOL. I.—NEW SER. 64, Reape, on a New Hemispherical Condenser. diaphragms to stop out the light in the right place of a Gillet’s, or perhaps still better, from its greater angle of aperture, a Powell’s condenser, we should approach perfection in resolving difficult markings under the deepest powers. My old black-ground illumination, which led to the forma- tion of valuable condensers by Messrs. Shadbolt and Ross, may be produced with very good effect by the hemisphere and a single aperture; and I feel sure that the members of our society will be much pleased with the brilliant definition and detail of a scale of Podura under this illumination and the half- inch object-glass. I have in my possession the same scale which my old and valued friend, Andrew Ross, saw with his first achromatic 1th, in his little workshop at St. John’s, Clerkenwell, and I shall never forget the expression of his astonishment. But the present half-inch is superior in all respects to that 4th. It is now generally known that I offer the hemispherical condenser as the special adjunct of the new half-inch object- glass of 90° aperture. Mr. Thomas Ross sent me his first object-glass of this new construction, for examination and report ; and I believe, like many others, he hesitated to give implicit eredence to my account of its working. As he was ignorant of the power of the ‘kettle-drum condenser,” he thought that the asserted resolution of that old microscopic nebula, the P. angulatum, under so low a power as a half-inch, even of large aperture, indicated the partiality of friendship rather than the severity of honest criticism. Accordingly I was summoned before a microscopic jury, consisting of Messrs. Leonard, Millar, Lobb, and Roper; and after sufficient and careful examination, Mr. Leonard, as the judge, decided that I might “take a rule nisi.”’ As the half-inch and the condenser had not only not flinched from any fair work, but had even trespassed on the domain of the 1th and the 1th, I thought that IJ would show at last what they could not do; and therefore, without the slightest expecta- tion of taking anything for my pains, I placed on the stage of the microscope a slide of the Amician test, the Navicula rhomboides, which was kindly presented to me by Mr. Powell, whose fine th, with its unequalled achromatie condenser, reveals the exquisite skill which is bestowed on this almost invisible work of the great Creator. It does one good, both mentally and morally, to review such a work as this; and, to my astonishment and delight, I witnessed its resolution under my new arrangement. It is necessary, in this instance, to use a deep eye-piece for attaining the requisite amplification ; and as eye-pieces are instruments for measuring the imper- Brapy, on the Seed of Dictyoloma Peruviana. 65 fections of object-glasses, this result led to a definite opinion as to the quality of the power employed. I will only add, that when combined with the hemispherical condenser and the whole series of eye-pieces, the new half-inch is a battery of microscopic powers, and will be a good substi- tute, in case of slender purses, for the =4,th, 79th, tth, and other fractions. I may therefore be permitted to congratulate our society on the valuable results consequent upon the attainment of almost unlimited aperture, combined with per- fect flatness of field, in powers as low as the $ and -4,th; and let it not be for sotten, that English opticians still take the lead in these improvements, which should yield honour as well as profit to themselves. On the Step of Dicryotoma Peruvtana, D.C., &c. By ty. GB. Brapy, 1.0.5. (Read June 12th, 1861.) THERE are few points of greater interest to the micro- scopist, or that better repay his attention, than the external character of the seeds of plants. Many, from their mere superficial beauty, have become popular show-objects ; but a deeper interest is awakened, and an almost boundless field of investigation is suggested, by such phenomena as those pre- sented by the peculiar spiral cells of the testa of Collomia, Ruellia, or Salvia; the curious hairs from the seeds of Cobza or Acanthodium ; the beautiful surface markings on those of Papaver, Lychnis, or Silene; the coma of Hoya and other Asclepiads; or the membranous wings so common amongst the Bignoniacee. That there are many new and valuable facts to be gathered from a systematic study of these structures, no one who has given much attention to them ean doubt, and I only regret that my own observations, though extending over a considerable time, have as yet been too desultory and disconnected to be of much practical value. Recently, however, a specimen was placed in my hands so peculiar in some of its characters that I have thought it might properly form the subject of a short notice. The seed of Eccremocarpus scaber, a half-hardy climbing plant, common in our gardens, is familiar to most as a microscopic object ; but as an acquaintance with this will 66 Brapy, on the Seed of Dictyoloma Peruviana. render the rest of my paper more intelligible, I may be allowed to advert to it in a few words. When mature, it is a roundish or kidney-shaped seed, about a quarter of an inch in diameter, thickest at the centre, and gradually thinner towards the outer edge, which we find ex- panded into a thin, membranous wing (Pl. VII, fig. 5). Careful examination shows that the cells on the outer layer of the testa, which appear on the body of the seed in the form of irregular projections, are, towards the circumference, excessively developed, especially in Jength, and it is in this way that the expansion alluded to is formed. The side walls of these elongated cells become much thickened in the process of growth, thus affording to the wing the necessary strength and firmness, whilst the front and back walls retain their original transparency, being marked only by a very delicate subspiral deposit. A glance at the accompanying sketch (fig. 6) will supply any deficiencies of this verbal description. This introduction will, I trust, render intelligible the more complicated structure which is observable in Dictyoloma Peruviana. A general idea of this beautiful seed may be gathered from fig. 1. Endlicher’s description of it, which is very defective and partially incorrect, runs thus :—~ Semima late reniformia, compressa, dorso in alas duas parallelas radiatim reticulatas, fibra marginali connexas expansa, sinu ventrali umbilicata.”” As we may infer from the above, it is broad, kidney-shaped, and flattened. Besides possessing a wing formed in a similar manner to that of Eccremocarpus, by the expansion of the testa round the edge, there are several succesively smaller, lateral wings in the same plane, the margins of which form a series of concentric rings over either surface of the seed. These smaller wings lie close to the surface, and appear almost like a continuous coat of connected cells ; indeed, those nearest the centre seem to be more or less connected through their entire length to the seed itself, the outer extremities only being raised above the general surface, thus keeping up the appearance of con- centric rings above alluded to. The alz, as they approach the circumference, become successively larger, and to a greater extent free. The sectional sketch, fig. 2, represents, as nearly as I can make out from the small materials at my command, the arrangement of the wings. But perhaps the structure of the ale themselves is the most remarkable feature in the case. Each wing appears to consist of a series of radiating fibres connected at their outer margin, the spaces between them being left quite open. ed GREVILLE, on New Diatoms. 67 Fig. 3 represents a portion of the outer sets of wings under a higher magnifying power, and this sketch will also serve to show their position with regard to each other. I was some time before I could satisfactorily account for this singular character, and it is only after a number of obser- vations on other winged seeds bearing more or less on my specimen that I am enabled to speak with confidence about it. The separate wings seem to be formed in the manner I have just described in reference to Eccremocarpus. The cells of the outer layer of the testa are developed to a great length, and the sede walls are thickened in the same way ; but the front and back walls, not being supported by deposit of any sort, are ruptured at a very early stage, and gradually disappear, leaving the side walls only as a sort of framework or skeleton. The frequent raggedness of the sides of the fibres is best accounted for in this way, and the appearance of one of the inner wings carefully removed from the seed (fig. 4) fully confirms this view, as it still retains portions of the delicate cell-wall only partially disintegrated. I had hoped that an examination of the ovules in a very early stage would have shown the outer wings entire, but in the only flower which I have had an opportunity of dissecting the ovary was too. immature to throw any light on the subject. Altogether, the specimen I have described reminds one strongly of the leaf of Ouwvirandra fenestralis, and though botanically the phenomena are not. identical, it loses nothing in interest by such association. In conclusion, I must acknowledge my thanks to my friend, Professor Oliver, for the specimen from which this notice is written, and Mr. Tuffen West for memoranda from seeds in his own collection bearing somewhat on the present case. Descriptions of New and Rare Diatoms. Series II. By R. K. Grevitzz, LL.D., F.R.S.E., &e. (Read June 12th, 1861.) Ry.tanpsta, n. gen., Grev. and Ralfs. FrustuLe simple, disciform, cellulose; disc with smooth rays, dilated at their base, and not reaching the centre. (No umbilical lines nor hyaline area.) | 68 GREVILLE, on New Diatoms. This remarkable genus appears to belong to the group re- presented by Asterolampra, but differs essentially in the ab- sence of umbilical lines and of the hyaline area, so conspicuous in all the discs referred to that genus. In the only known species of the genus now proposed, the valve is cellulose, very much in the manner of Coscinodiscus radiatus ; and the rays, two in number, have their dilated bases separated by a con- siderable interval, and have no connection whatever with each other. This singular diatom is worthily dedicated to my friend Thomas George Rylands, Esq., of Heath House, Warrington, a very acute observer, who communicated it to me soon after its discovery by Mr. Ralfs. Rylandsia biradiata, n. sp., Grev. (Pl. VIII, fig. 1). Hab. Barbadoes deposit, very rare; John Ralfs, Esq., T. G. Rylands, Esq., Dr. Greville. A considerable number of specimens of this curious disc have now been seen, and it is satisfactory to know that it is quite constant to its characters. The cellules in the centre of the valve between the bases of the rays are large; they then — suddenly become smaller, and decrease gradually in size as they radiate to the circumference. The rays are broadly cuneate at the base, and linear as they reach the margin ; they appear to be tubular, as in Asterolampra, and a faint shadow indicates the continuance of this structure through the middle of the dilated bases. In asingle instance the two valves occurred in situ, the rays of the lower crossing those of the upper valve. CoscINODISCUS. Coscinodicus symmetricus, n. sp.,Grev.—Granules radiating, distinct, all equal and equidistant; seven of the radiating lines extending from the centrical granule to the circum- ference; margin striated. Granules 10 in ‘100’; marginal strie 15 in ‘001’. Diameter :0031”. (Pl. VIII, fig. 2.) Hab. Barbadoes deposit; excessively rare. One of the most beautiful of the granuliferous group of Coscinodisci, and well characterised by the equal distribution of the granules. It is also distinguished by the manner in which the radiating lines are arranged. From the central granule proceed seven long lines, and within the compart- ments so formed the next two longest are disposed, one on each side, so as to form two equal sides of the triangle, and so on until the whole space is filled up. CRESSWELLIA. Creswellia superba, n. sp., Grev.— Valves hemispherical, GREVILLE, on New Diatoms. 69 depressed, with a broadly expanded- hyaline margin; areola- tion large; connecting processes robust, spine-like, situated nearer to the margin than the apex. Diameter -0024" to 0054". (PI. VIII, figs. 3, 4, 5.) Hab. Barbadoes deposit ; frequent. A splendid species, with very large areolation. Average specimens possess from six to eight connecting processes, but examples occur with from four or five, up to the giant repre- sented at fig. 5, with nineteen. I have never seen Ehrenberg’s Stephanopyxis diadema; but if Kutzing’s definition be correct, “‘ disci medii depressi annulo dense denticulato”—my present diatom must be distinct. Kutzing, besides, yives the number of teeth in the crown as thirty, whereas it is a very rare circumstance indeed to see so many in Cresswellia su- perba as appear in fig. 5. Evopia. Euodia Barbadensis, n. sp., Grev.—Frustules semilunate, ends slightly produced, lower margin straight; surface cellu- lose, with a small, irregular, central blank space. Distance between the aneles 0015” to 0020”. (Figs 6, 7.) Hab. Barbadoes deposit ; extremely rare. Valve yellowish ; short, vein-like lines are given off from the margin, sufficiently conspicuous in the larger speciraens, but less so in small ones. The upper margin is conical-con- vex, so as to give the frustule very much the outline of a cocked hat. Cellulation rather large, but under a low power appearing as granules. TRICERATIUM. | Triceratium cornutum, n. sp., Grev.—Valve (4-angled ?) with straight sides and sharp angles furnished with strong, horn-like processes ; surface minutely granulose, in lines ra- diating from the centre, on which are three spines; granules at the margin 15 in :001”. Distance between the angles 0015". (Fig. 8.) Hab. Barbadoes deposit ; excessively rare. The only frustule, a very perfect one, which has come ehder my notice, has four angles with exceedingly strong, horn- like processes, which, as they cast a dark shadow, render the frustule conspicuous. The granules are very minute in the centre, but increase in size as they radiate to ‘the margin. It is quite distinct from the few species already described, having spinous lateral surfaces. Triceratium productum, n. sp., Grev.—Valve punctate ; 70 GREVILLE,.on New Diatoms. angles produced, capitate ; centre divided into compartments by radiating, vein-like veins. Distance between the angles 0027”. . (Fig. 9.) Hab. Barbadoes deposit ; excessively rare. | This beautiful species is evidently related to T. cba and T. venosum; to the former very closely, while, at the same time, it is abundantly distinct; the truly capitate, pro- duced angles taking the place of the broad, truncate angles of that diatom. Triceratium inconspicuum, nu. sp.,.Grev. —Minute, sparsely punctate; angles of the valve semicircular, subtruncate, separated from the centre by a transverse line; centre bordered with a row of puncta. Distance between the angles. 70005". (Fig. 10.) Hab. Barbadoes deposit ; excessively rare. Of this exceedingly minute species I have seen half g a dozen specimens, all of which have four angles. In its cha- racters it comes very near to some varieties of T. brachiatum, but is separated by its size alone, which scarcely exceeds that of T. exiguum. Triceratium delicatum, n. sp., Grev.—Minute; valve with slightly concave sides and broadly rounded angles filled up with transverse rows of fine puncta; centre containing a ‘pale, obtusely triangular band, within which is a triangular spot, bordered with puncta. Distance between the angles “*O012".. - (Fig. 11.) _ Hab. Barbadoes deposit; excessively rare. A minute species, difficult to define in few words. The eye is first impressed with the pale (blank), triangular band, which exactly fills up the centre of the valve by the angles reaching to the concave margin, and, consequently, separating the angles of the valve from the parts within. In the central spot, which is edged with a row of distinct puncta, I have -been unable to trace any particular structure. A peculiar feature in this little diatom is a considerable space between the sides of the pale band and the transverse rows of puncta which occupy the angles. These puncta also gradually de- crease in size as they approach the apex. Triceratium labyrintheum, un. sp., Grev. — Valve with rounded angles and somewhat convex sides, the centre having a network of flexuose, widely anastomosing, vein-like lines, the mclosed spaces being finely punctate. Distance between the angles :0023". (Fig. 12.) | Hab. Barbadoes deposit; excessively rare. Of all the curious Triceratia which have been discovered in this inexhaustible deposit the present species is one of the GREVILLE, on New Diatoms. ri most remarkable. About half a dozen examples have been observed. The interval between the margin and the central labyrinth of lines is blank, with the exception of a few short, vein-like lines given off from the central network, some of which nearly reach the margin. — In this, as in many other in- stances, a figure will convey a better idea of the object than the most elaborate description. Triceratium areolatum, n. sp., Grev. —Valve with slightly concave sides and acute angles ; surface covered with rather large, circular areole, while very short, vein-like lines project from the sides of the valve. Distance between the angles 0026”. (Fig. 13.) . Hab. Barbadoes deposit ; extremely rare. I do not know any member of the genus with which this diatom can be compared, unless it be 7. acutum, Ehr., with which it agrees in the rather peculiar areolation. From that species, however, it differs in the sides of the valve being decidedly, although slightly, concave, and in the angles not being in the smallest degree elongated. The short, vein-like lines present, in addition, a conspicuous differential cha- racter. Nevertheless, I am not certain of its being distinct. Triceratium tessellatum, n. sp., Grev.—Valve with straight sides and rounded angles, somewhat convex in the centre; surface filled with subquadrate, large, more or less concentric granules, becoming smaller at the angles; margin with a row of minute granules, 11 im ‘001’. Distance between the angles 0025". (Fig. 14.) Hab. Deposit on the banks of Pertuxent River, near Not- tingham, Maryland, United States. Distinguished by the large size and more or less square form of the granules, especially those of the convex centre. Smaller granules completely fill up the angles. In some ex- amples the convexity of the centre is scarcely at all apparent. Triceratium robustum, n. sp., Grev.— Valve with straight or very slightly concave sides and rounded angles with pseudo-nodules ; surface filled with irregularly shaped, coarse granules, those in the circumference of the convex centre and at the angles small, the rest large. Distance between the angles -0030’ to 0040’. (Fig. 15.) Hab. Cove, Calvert County, Maryland, United States. A strong, coarse-looking species, with a large, clear, pseudo- nodular space at the angles. The granules are very irregular, small ones being often mixed with the large ones. Some- times a concentric arrangement is conspicuous, but in other cases it is very partial, being most distinct between the con- vex centre and the angles, where also the largest granules 72 GREVILLE, 02 New Diatoms. occur. This diatom is subject to occasional distortion, several examples having occurred to me in which the sides were of very unequal lengths. : Triceratium Browneanum, n. sp., Grev.—Small; valve with straight sides and rounded angles with obscure pseudo- nodules ; surface filled up with small, round, equal, irregularly disposed granules. Distance between the angles about 0020”. (Fig. 16.) Hab. In mud, Savannah, Georgia, U.S. Probably not a rare species, as it occurs tolerably abundantly in a slide kindly communicated to me by my friend, Mr. George Mansfield Browne, of Liverpool. It is well marked by the equal size throughout the entire valve of the round granules, which, although not crowded, are rather closely situated. The angles are thickened, but can scarcely be said to possess a pseudo- nodule. | Triceratium ? blanditum, n. sp., Grev.—Sides of valve deeply concave ; angles broadly rounded ; centre with a small, blank space; granules conspicuous, subremote, equal, forming straight, equidistant, parallel lines. Distance between the angles in the four-angled frustule 0020”. (Fig. 17.) Hab. Barbadoes deposit; excessively rare. A very striking object, which I introduce with some hesita- tion as a Triceratium. Amphitetras, however, is now ad- mitted to be separated from that genus by a very slender line. I have seen only two frustules, both of which are four-angled, and very conspicuous for the equal size. of the granules, their equidistance, and the perfectly straight, parallel lines in which they are arranged. The small, circular, blank space is only defined by the absence of granules. There is also a small, vacant space opposite to each concavity of the valve. This species may have some affinity with Amphitetras parallela of Ehrenberg, found im a fossil state in Greece. . CocconkEIS. Cocconeis Grantiana, n. sp., Grev.—Very minute; valve elliptic, smooth, with a slender median line and nodule, the margin furnished with a moniliform row of lange, oblong granules. Length 0011". (Fig. 18). Hab. On marine shells, Macduff; John Grant, Esq. A beautiful little object, the smooth disc rendering the marginal row of brilliant, bead-like granules more conspicuous. Mr. Grant, to whom I am indebted for a specimen, aptly compares the entire frustule to a jeweller’s ornament set with gems. | GREVILLE, on New Diatoms. 73 Cocconeis granulifera, n. sp., Grev.—Minute, elliptic- oblong, with a median line and rather large nodule; disc with remote radiating lines of large, oval granules (three in each line), reaching from the median line to the margin. Radiating lines 5in ‘001. Length 0015”. (PI. VIII, fig. 19.) Hab. On Pectens, Carrickfergus ; John Grant, Esq. The characteristic features of this little species are the very large granules, the small size of the valve being considered (three only being found in each line), and the distance between the radiating lines themselves, there being only about thirteen on each side. Both this and the preceding appear to be clearly distinct from all described species. Descriptions of New and Rare Diatoms. Series III. By R. K. Grevitrze, LL.D., ¥.R.S.E., &e. (Read June 12th, 1861.) BricHtwe ui, Ralfs. Brightwellia elaborata, n. sp., Grev.—Cellules of coronal circle roundish ; border composed of uniform, radiating lines, connected by numerous transverse lines. Diameter :0034”. LPL EX » fie...) 7 Hab. Barbadoes deposit ; excessively rare. This exquisite diatom bears a considerable general resem- blance to Brightwellia Johnsoni of Ralfs, MS., being of the same size and having a very similar coronal circle of large cells. But an essential difference is found in the structure of the border. In B. Johnsoni it is composed of radiating lines of round cellules, which decrease in size from the corona tothe margin, where they are quite minute; while at irregular intervals dark, strong, radiating lines occur, which appear to project like a spinous ridge, as in my Coscinodiscus armatus. In the present species, on the contrary, the border is formed by a close series of straight, uniform, radiating lines, connected by transverse (or concentric) lines or bars, which thus pro- duce rows of quadrate cellules, increasing in size from the co- ronal circle to the margin. Two of the radiating lines, with their connecting bars, might not unaptly be compared toa microscopic ladder. 74 GREVILLE, on New Diatoms. This beautiful genus appears to be a very natural one ; its characteristic feature being the coronal circle of large cellules, and the curved or spiral arrangement of the cellules within the circle. The typical species, B. coronata, has never, I believe, been found entire, the greater portion of the border being always absent. On two occasions only have I obtained a fragment in which, along with part of the corona, was a portion of perfect margin. Do the coronal cells in this species invariably retain their oblong character? Hxamples have certainly come under my notice in which they were more round than oblong, but I unfortunately omitted to mark them. It is, however, by no means improbable that the valves referred to may belong to an undescribed species. TRICERATIUM. Triceratium notabiiis, n.sp., Grev.—Large. Valve punctate, with straight sides; angles broad, much produced, dilated, - oblong or somewhat rhomboidal, with a conspicuous pseudo- nodule; centre convex, with radiating puncta and several spines. Distance between the angles ‘0025” to -0040”. (Figs. 2, 3.) Hab. Barbadoes deposit; rare. Of this fine diatom above a dozen examples, including broken specimens, have come under my observation. It is evidently related to T.coniferum, but isa much larger species, and conspicuous for the very produced angles, which are equal in length to the straight sides of the valve. The prevailing form of the angle is rhomboidal, but it is occasionally oblong, as in fig. 3. The centre of the valve is convex, and the puncta radiating as in T. coniferum, a character omitted to be brought out in the figure of that species in the ‘ Microscopical Journal.’ The centre is also furnished with spines, no fewer than seven being present in fig. 3, while in the specimen represented at fig. 2, two are situated at the base of each angle. The Barbadoes deposit has yielded me several other frustules, which formahighly characteristic little group, of which T. coniferum may be regarded as the type, but whether some of them ought to be considered species or mere varieties is extremely difficult to say. They all agree in the radiating - punctation, convex centre, spines, and pseudo-nodules, but differ considerably in form and relative proportions. Of these diatoms figures will be given on a future occasion. | Triceratium microcephalum, n. sp., Grev.—Valve with con- vex sides and slender, produced, subcapitate angles, furnished with pseudo-nodules ; entire surface, except a small, central, GREVILLE, on New Diatoms. 75 circular space, minutely punctate. Distance between the ngles 0026”. (Fig. 4.) ab. Barbadoes deposit ; excessively rare. In general outline this species bears a close resemblance to T. productum of my Series II, but differs essentially in the absence of all vein-like lines. From T. capitatum of Ralfs it is removed by the much larger size, shorter angles, the absence of spines, and by the minute and close punctation of the whole surface. Triceratium insignis, n. sp., Grev.—Large. Valve with con- cave sides, and broadly rounded angles, furnished with minutely punctate pseudo-nodules ; surface filled with radiat- ing lines of minute, distinct granules, except a small, central, blank space; margin with short, broad striz, 9 in 001”. Dis- tance between the angles ‘0034. (Fig. 5.) Hab. Barbadoes deposit; excessively rare. A remarkably fine and ornate species, possessing most dis- tinctive characters. At first sight the angles have the appear- ance of being separated from the centre by a transverse line, but this is not the case. The effect is produced by the radiat- ing lines of granules curving up the prominent angles, and being viewed, as it were, in prospective, the extremities of the lines form a transverse row of dark points. A very con- spicuous feature in the valve is the termination of what are doubtless strong, broad striz in the front view,’and which are curved over the edge of the valve in the side view. The ra- diating lines of granules which closely cover the surface do not quite reach the margin, but leave a narrow, blank space. Triceratium rotundatum, n. sp., Grev.—Small. Valve with deeply concave sides and broadly rounded angles, the ends of which are filled with minute puncta, bordered with a few larger ones; centre blank, surrounded by an irregular, tri- angular band of still larger granules, between which and the granules of the angles is a transverse, blank space; concave margins, with afew distant, large granules. Distance between the angles -0020". (Fig. 6.) Hab. Barbadoes deposit; extremely rare. About the size of T. castellatum and T. Westianum ; but the angles do not form segments of circles as in those species, being “aly broadly rounded. About six granules compose the marginal row in the concavities of the valve. Triceratium amenum, n. sp., Grev.—Small. Valve with straight sides and rounded, incrassated angles; centre some- what convex, with subremote radiating puncta, which gradu- ally increase in size from the centre to the circumference. Distance between the angles about -0024”. (Fig. 7.) 76 GREVILLE, on New Diatoms. Hab. Nottingham deposit, Maryland, U-S. Not rare, yet I cannot refer it to any described species. It is a neat and brilliant little diatom. The puncta or minute granules are rather distant, the largest bemg those imme- diately external to the raised centre; in the angles they again become smaller. The angles themselves are frequently, though not invariably, slightly dilated, as in fig. 7, and are thickened in substance, but no distinct pseudo- nodule is perceptible. Triceratium obscurum, n. sp., Grev.—Small. Valve thin and delicate, with nearly straignt sides and rounded angles; puncta equal, very minute, radiating in straight lines. Dis- tance between the angles ‘0024. (Hig. 8.) Hab. South Naparima deposit, Trinidad. Contour exactly resembling that of 7. condecorum, but the radiating lines of puncta are perfectly straight. The puncta are also somewhat more minute. . Triceratium Harrisonianum, n. sp., Norman and Grev.— Large. Valve with convex sides and slightly produced, rounded angles; pearly granules forming a marginal band of radiating rows, and thinly scattered over the ample central space, in which is a conspicuous network of large, elongated, radiating cellules, sending down lines between the rows of granules to the margin; rows 4in 001”. Distance between the angles ‘(0070”. (Fig. 9.) Hab. Barbadoes deposit Saati Estate); exceedingly rare ; George Norman, Esq. A ‘truly splendid diatom, belonging to a small, very natural group, and, as is frequent in such cases, extremely difficult to define satisfactorily. It may be, indeed, that most of them constitute but one species; and if so, it becomes all the more necessary that they should be carefully figured and described. This I hope to be able to do in a future series. J. mar- garitaceum, described by Ralfs in the last edition of ‘Pritchard’s Infusoria,’ is the only one hitherto published, and, as the first known, may stand as the type. It is comparatively a small species, the distance between the angles being only about 0030”, often less. All the members of the group, however, possess the same structural arrangement, the central portion of the valve being composed of large, radiating, elongated cellules, which towards the margin become smaller and quadrangular, each of the quadrangular cellules containing a round, pearly granule. In none of the species are these characters seen so conspicuously as in our new T. Harrisonianum. The outline of the valve in these species varies considerably. According to Ralfs, the sides of the valve in 7. margaritaceum are straight. GREVILLE, on New Diatoms. 77 or slightly convex, and the angles rounded. Inall the speci- mens I have seen they are straight or very nearly so, but other valves in my possession have the sides decidedly con- vex, along with a generally distinct aspect at once appreciable by the eye, but difficult to convey in words. Among other characters, the value of which I do not at present venture to estimate, is the slightly produced angle in combination with the more or less convexity of the side, as seen in the present and following species. This feature has not been observed in T. margaritaceum, and may eventually be found to facilitate the diagnosis of these most perplexing diatoms. We have much pleasure in dedicating this fine species to Mr. Harrison, of Hull, who has devoted much attention to the microscopical investigation of the Diatomacee. Triceratium giganteum, n. sp., Grev.—Large. Valve with slightly convex sides, and rounded, somewhat produced, angles; pearly granules, forming a marginal band of radiat- ing lines; central space filled with minute, scattered spines. Distance between the angles ‘0066". (Fig. 10.) Hab. Barbadoes deposit; exceedingly rare; Christopher Johnson, Esq., George Norman, Esq. Scarcely less splendid than the preceding, and more remarkable on account of the singular spinulose, central surface. Itis a robust species, with large, round, somewhat flattened, granules, and a very strong margin. For the specimen in my cabinet, from which my drawing was made, I am indebted to the kindness of my friend, Mrs. Bury. The only other frustule hitherto discovered, so far as I know, is in Mr. George Norman’s collection. AMPHITETRAS. Amphitetras minuta, n. sp., Grev.—Minute. Valve with deeply concave sides and rounded angles; lines of very minute puncta, radiating from the centre to every part of the os Distance between the angles ‘0014. (Fig. Hab. Nottingham deposit, Maryland, United States. I have seen several frustules of this inconspicuous little diatom, which is extremely liable to be overlooked. All are four-angled, and I venture to place it provisionally in the present genus. Payer hee) 5 TRANSACTIONS. Descriptions of New and Rare Diatoms. Szrizs IV. By R. K. Grevitiz, LL.D., F.R.S.E., &e. (Read June 12th, 1861.) STICTODISCUS. Stictodiscus Californicus, n. sp., Grev.—Puncta equal, large, in rows of a single series; rays obscure, terminating in conspicuous, linear-oblong bases within the broad margin ; central puncta somewhat remotely scattered. Diameter "0088". (Pl. X, fig. 1.) Hab. Monterey stone. A genuine Stictodiscus, distinguished from S. Johnsonianus (which it resembles in the puncta, being arranged in single rows) by the obscure and much shorter rays, by the broad margin, and linear-oblong bases of the rays. Although the latter are decidedly obscure compared with the same parts in the other species, a careful adjustment shows their presence, as well as the anastomosing lines towards the centre, which exist in S. Buryanus and S. Johnsonianus. When the sur- face of the disc is exactly in focus, the puncta appear simple ; but by slightly lowering the focus a pore becomes visible in the middle of each punctum; and on viewing the valve from within, the pores are very conspicuous, and placed on the summits of little circular convex cavities (plane on the outer surface, convex on the inner surface, of the valve), strongly resembling the discs in the woody fibre of the Coniferee, which are themselves little, plano-convex boxes, with an orifice. The border of the disc is bounded by a row of minute puncta. The number of rays is upwards of forty. Stictodiscus Kittonianus, n. sp., Grev.—Disc umbonate, with a central nucleus; rays numerous; puncta minute, equal, forming a double series in each compartment, and closely covering the central space. Diameter about -0020”. (Figs. 2, 3.) VOL. IX. g 80 GREVILLE, on New Diatoms. Hab. Nottingham deposit, Maryland, U.S.; Richmond, Virginia, F. Kitton, Esq. | A small but beautiful species, with very numerous puncta of equal size throughout, and especially distinguished by the umbonate surface and central nucleus of the disc. The rays terminate simply at the margin, which is unmarked by puncta or striz of any kind. My best thanks are due to Mr. Kitton for a specimen exhibiting the front view, which | forms avery interesting object. It shows the frustule to be composed of two unequally umbonate valves, each of them furnished with a broad, folded-down edge, as in the lid of a pul-box, which edge is divided into large, square cellules, corresponding in number with the rays and compartments as seen in the side view. ‘These cellules are the more con- spicuous from being destitute of any kind of sculpture. Mr. Kitton informs me that, in addition to the localities above recorded, he has observed this diatom in the Pescataway, Rappahannock, and Monterey deposits. CoscINODISCUS. Coscinodiscus patelleformis, n. sp., Grev.—Central granules minute, round, numerous, from which proceed a number of rays, terminating about half way between the centre and the margin in an irregular circle of minute, dark, spine-like tubercles, beyond which are radiating lines of sub-contiguous granules increasing in size to the circumference; margin with a row of minute puncta. Diameter about ‘0034’. (Fig. 4.) Hab. Barbadoes deposit ; very rare. This curious diatom has much the appearance, under a low magnifying power, of Coscinodiscus biradiatus, with some adventitious matter adhering to the disc. Indeed, I passed over several specimens under this impression; but I was at length induced to examine them more carefully, and per- ceived that several important characters indicated a distinct species. The radiating lines which occupy the outer half of the disc are composed of coarse granules almost touching one another, and increasing in size as they approach the margin. But a more remarkable feature is found in another series of radiating lines, occupying not exactly the centre, but what may be termed the crown of the disc, and terminating about half way down. These have all the appearance of a separate structure, closely united to the original one, the whole bearing a strong resemblance to some of the Patelle. The last-mentioned series, or, as they may be called, the coronal GREVILLE, 0n New Diatoms. 81 rays, are somewhat irregular in length, and consequently do not form an exact circle. They terminate in one or oc- casionally im two spinous processes, which are evidently analogous to those with which some of the rays in C. armatus and other diatoms are furnished. TRICERATIUM. The first seven of the following species constitute a very interesting and exceedingly natural little group, and present an excellent illustration of the difficulty of distinguishing between closely allied forms. Without attempting to dog- matise upon the questio vexata of ‘ What is a species?” we may safely venture to figure and describe, with benefit to science, such organisms as we have reason to believe exhibit characters by which they may at any time be identified. Such characters are necessarily sometimes minute, but are not thereby of less value. In a systematic work the species about to be described would arrange themselves at once into two sections—the first containing those which have simple (not striated) margins and the central triangular space filled up with radiating lmes; the second those which have striated margins and the central triangular space blank. There is another peculiarity, also, which separates the two sections. In the first the angles of the central triangle are lengthened out until they reach the pseudo-nodule; in the second the angles are not lengthened out, but each is kept with a short strong line which never reaches the pseudo- nodule, but terminates in a fork more or less connected with other vein-like lines. I have not satisfied myself about the nature of the short line referred to. In T. pulcherrimum (fig. 6) it takes the form of a small spine, distinctly seen within the pseudo-nodule. In 7. marginatum it may also be seen, but with some difficulty, through the intervening lower pseudo-nodule. These little spines must be regarded as analogous to the short lines holding a similar relative position to the angles of the inner triangle in the species of the second section. In some instances, especially in 7. varie- gaium, I have observed the short line to be slightly raised, suggesting the idea, which is confirmed by the position of the spine in the species of the first section, that this organ belongs properly to the framework of the inner triangle, and that the lines which appear to emanate from it belong to the system of costz or vein-like lines which divide the border of the valve into compartments. Triceratium marginatum, Br.—Valve with slightly convex 82 GREVILLE, on New Diatoms. sides, rounded angles, double pseudo-nodules, and simple margin; centre a triangular space, filled with radiating moni- liform lines; border divided by transverse lines into punctated ee eS Distance between the angles, about ‘0026”. ig. 5.) Triceratium marginatum, Brightw., ‘Mic. Journ.,’ vol. iv, p- 275, pl. xvi, fig. 13s - Ralis; im ‘ Pritch:) Intas isan, p. 854. Hab. Barbadoes deposit, chiefly from Cambridge Estate ; extremely rare; T. Brightwell, Esq., F. Kitton, Esq., Dr. Greville. Although this fine species has been, in all essential points, correctly figured in Mr. Brightwell’s paper quoted above, I have a twofold purpose in introducing another illustration in this place. It is very desirable that the student should be able at once to compare with it the new and allied species I am about to describe, most of which I have received under the same name. I wish, besides, to represent a structural arrangement which does not appear in Mr. Brightwell’s figure. This consists of a circular, blank space surrounding the apex of the angle of the inner triangle and the inferior pseudo-nodule. It contains no puncta; and several faint, short lines, and two dark and longer ones, radiate from it. It is probable that this character may be more or less obscure in some individuals, as it is by no means conspicuous in Mr. Kitton’s specimen, which he has kindly permitted me to examine. It would appear that no dependence can be placed on the number of lateral costa. In Mr. Kitton’s example there are two on each of two sides, and three on the other. In my own the number on two sides is similar, but there is only one on the third side. Mr. Brightwell’s figure shows four on each of two sides and three on the other. With regard to the radiating lines of the inner triangle, I am in- clined to consider them as modified coste. Much depends upon the angle at which they are viewed. In my own specimen they have all the appearance of lines of puncta, but in Mr. Kitton’s valve the costate character comes clearly out, with the addition of being nodulose, especially as the coste approach the margin of the inner triangle. Triceratium pulcherrimum, un. sp., Grev.—Valve with slightly convex sides, rounded angles, and simple margin ; centre a triangular space, filled with radiating coste; border divided by transverse lines into punctated compartments, which are continued round the large, oblong pseudo-nodules. Distance between the angles ‘0045”. (Fig. 6.) Hab. Barbadoes deposit, C. Johnson, Esq.; exceedingly rare. GREVILLE, on New Diatoms. 83 One of the most beautiful diatoms known, and closely allied to the preceding. In this case the radiating lines of the centre are genuine costz, each of which, as it terminates at the margin of the inner triangle, becomes capitate, pro- ducing an exquisitely ornamental effect. The pseudo-nodules are large, flat, and oblong; and an approach is made to the double pseudo-nodule of the preceding species, by their being traversed by two fine oblique lines, which, meet at the apices of the angles of the inner triangle ; and what brings the approach still closer, is the fact that it is the division next the angle of the valve only which is punctate. A re- markable peculiarity consists in the pseudo-nodules not being situated in the extreme angle, as in the other species of the group, but leaving space for the lateral cost to be visibly continued round them. These costz are widely separated throughout the greater length of the border, but imcrease rapidly in number as they turn round the angle, so that there are about twenty on each side. The angles of the inner triangle are lengthened out until they enter the punc- tate portion of the pseudo-nodule, and terminate in a short spine. In thisand the preceding species tlie puncta in the lateral compartments are rather widely scattered. Triceratium Abercrombieanum, n. sp., Grev.— Valve with nearly straight sides, obtuse angles, and striated margin; centre a blank triangular space; border divided by transverse costz into punctated compartments; a short line from each angle of the central triangle terminating in a wide fork with incurved apices, a faint, undulating line passing along the middle of each border. Distance between the angles, about 0023". (Figs. 7—9.) Hab. Barbadoes deposit, C. Johnson, Esq., Dr. Greville; extremely rare. At a hasty glance this might readily pass for a variety of the preceding species; but the presence of a striated margin, and the totally different centre, immediately dispel the impression. The pseudo-nodule, besides, is single; and although im one instance (fig. 9) the fork of the apex of the short line terminating the angles of the central triangle forms an enclosed, roundish space, instead of remaining open, it is unconnected with the pseudo-nodule, and contains puncta. A remarkable character in this species is a fait undulating line which passes along the middle of the border, commencing at the outer angle of the fork above mentioned, and ending at the corresponding point in the opposite angle of the valve. This line, which, although faint, may be traced without any difficulty, I have found uniformly present in the four specimens 84 GREVILLE, on New Diatoms. which I have had an opportunity of examining. By a reference to the plate it will be perceived that some variation is liable to occur in the lines at the angles, as well as in the number of the lateral coste. The puncta are considerably more numerous than in 7. marginatum. I have much pleasure in dedicating this diatom to my acute correspondent, Dr. Abercrombie, of Cheltenham. Triceratium inopinatum, n. sp., Grev.—Valve with nearly straight sides, rounded angles, and striated margin ; centre a blank triangular space; border divided by transverse costze into minutely punctated compartments; a short line from each angle of the central triangle terminating in a small, roundish compattment, joimed to the pseudo-nodule; no undulating line along the border. Distance between the angles ‘0020". (Fig. 10.) Hab. Barbadoes deposit ; extremely rare. The only question which can arise relative to the validity of the present species is whether it be not a variety of the preceding. Had the separation been proposed on account of the apparently double pseudo-nodule alone, I should have felt some hesitation. It might have been said that in one of the varieties of I. Abercrombieanum the short lines proceeding from the angles of the central triangle terminate in enclosed spaces, owing to the incurved apices of the fork becoming united ; and that if these enclosed spaces had been pushed forward to a junction with the pseudo-nodule, we should just have the appearance exhibited by the diatom now under consideration. It may be remarked, however, that the enclosed spaces above mentioned preserve their relative dis- tance from the pseudo-nodule, as distinctly as if the apices of the fork had remained open. In the present species there is, at first sight, the appearance of an actual double pseudo- nodule; but it is an appearance only, the second one being merely the fork of the short line meeting at the base of the pseudo-nodule, and thereby indicating a different relative position of the parts from what occurs in the preceding species. In addition to what has been said, the total absence of the undulating line so remarkable in the border of that diatom seems to confirm the view I have taken of the pro- priety of regarding 7. inopinatum as distinct. Triceratium approximatum, n. sp., Grev.—Valve with straight sides, obtuse angles, and striated margin; centre a blank, triangular space; border divided by transverse costz into punctated compartments ; a short line from each angle of the central triangle terminating in a wide, shallow fork ; pseudo-nodule single, sending out two spurs from the base ; GREVILLE, 0n New Diatoms. 85 no undulating line in the border. Distance between the angles ‘(0029”. (Fig. 11.) Hab. Barbadoes deposit ; excessively rare. A fine species, coming nearest to 7. Abercrombieanum, but wanting the undulating border line. The fork referred to in the specific characters here assumes a Pafera-like form. Whether any dependence can be placed on the two little spurs at the base of the pseudo-nodule, a character I have not observed in any other species of the group, it is impossible at present to say. The puncta are numerous. Triceratium gratiosum, n. sp., Grev.—Valve with slightly convex sides, obtuse angles, and striated margin; centre a triangular, blank space; border divided by'transverse costz into closely punctated compartments ; a short line from each angle of the inner triangle terminating im a fork, from the centre of which spring two other lines, curving outwards to the margin. Distance between the angles, 0029" to :0035”. (Figs. 12, 13.) Hab. Barbadoes deposit ; extremely rare; George Norman, Esq., Dr. Greville. A very elegant species, closely and conspicuously punctate. The arrangement of the vein-like lines at the angles is pecu- har, and serves at once to distinguish it from all its allies. Two lines spring from a point within the fork already men- tioned, near its base, and curve gracefully outward until they reach the margin. In the examples which I have examined, the lateral costz alternate more or less regularly with im- perfect ones, extending about half-way across the border. Triceratium variegatum, nu. sp., Grev.— Valve with straight sides, obtuse angles, and striated margin; centre a blank, triangular spaee; border divided by transverse cost into very minutely punctated compartments; a short line from each angle of the central triangle terminating in a deep, campanulate fork, the lines of which reach the margin. Distance between the angles, ‘0027". (Fig. 14.) Hab. Barbadoes deposit; excessively rare; George Nor- man, Esq. Of this beautiful diatom I have seen only a single specimen ; but it differs so materially from all the preceding, that no doubt whatever can exist regarding its claim to being ranked as a distinct species. It will be recognised at once by the graceful campanulate or vase-like compartment at each angle of the valve, which is very minutely, yet more dis- tinctly punctate than the border. A very minute, deflexed line may also be seen given off externally on each side from near the base of this compartment. 86 GREVILLE, on New Diatoms. Triceratium nebulosum, nu. sp., Grev.—Valve with concave sides and broadly rounded angles, the ends of which are filled with a cloud of minute puncta; centre occupied with an indefinite cluster of small puncta, while larger ones are remotely scattered over the rest of the space. Distance between the angles 0082”. (Fig. 15.) Hab. Barbadoes deposit ; exceedingly rare; George Nor- man, Esq. This species bears some resemblance in general outline to T. trisulcum of Bailey; figured in Pritchard’s ‘ Infusoria,’ 4th edit., pl. vii., fig. 27; but there are no transverse lines separating the angles from the centre. It is otherwise nearly allied to the same diatom, in the angles being crowded with minute puncta and in those of the centre being remotely scattered. These latter, however, are more numerous than in Professor Bailey’s species, and there is, besides, a marginal line of irregularly disposed and more closely approximated puncta in the concave sides of the valve. It is also allied to my 7. rotundatum, a vouch smaller species, from which it differs in the sides being much less deeply concave, in the absence of the single lateral row of large granules, and in the arrangement of the central granules generally. AMPHIPRORA. Amphiprora conspicua, n. sp., Grev.—Front view broadly winged, much constricted, truncated at the ends; a row of linear nodules at some distance within the margin; strice conspicuous, about 18 in ‘001”. Length -0046". (Fig. 16.) Hab. Sierra Leone, F. Kitton, Esq. The finest species, perhaps, of the whole genus; allied to A. alata, but quite distinct. In the first place, the frustule is far from being equally hyaline; and instead of the striz being perceived with some difficulty, they are rather coarse and very conspicuous. Then, in A. alata the number of striee (which I have been unable to ascertain satisfactorily for myself) is given by Smith as 42 in 001", which is adopted by Ralfs in the last edition of Pritchard’s ‘ Infusoria ;’ but in our new species they may be set down at 18 in ‘001". I have found them vary a little, but I assume this number as the average. Again, a certain number of the striz swell into a sort of linear nodule at some distance within the margin, and the line thus formed, following the marginal curve, con- stitutes a most peculiar and striking character. There seems to be no fixed rule as to the proportion of striz which exhibit GREVILLE, on New Diatoms. 87 this feature. Sometimes it is every fourth, at others every third striz. In addition to these differences there is yet another, in which the diatom under consideration agrees with A. pulchra of Bailey (‘ Mic. Obs. in South Carolina, &c.,’ p. 38, pl. ui, figs. 16—18), the striz near the margin being punctate. The surface of the valve is undulate, so that a portion only is in focus at one time, and the striz conse- quently appear to decussate obliquely im waving lines. I may add that, although I have seen a number of specimens, T have never observed one in the twisted state so common in A, alata. VoL, 1X. A , 4 Z t ss sie | Tans Moor Se VHINS M. Taffen West sc TRANSACTIONS OF MICROSCOPICAL SOCIETY. DESCRIPTION OF PLATE I, Illustrating Mr. Lobb’s paper on the Self-division of Micras- terias denticulata. Fig. 1.—Micrasterias denticulata in the first stage of self-division. 2.— 5 ‘ in the second stage of self-division. 3.— ” » » in the second stage of self-division, the endo- chrome coming in differently to what it does in figure. 2. A.— be a in the. third, stage of self-division. 5.— 2 re in the fourth stage of self-division. 6.— ie - in the fifth stage of self-division. — - » _ Self-division completed. TRANSACTIONS OF MICROSCOPICAL SOCIETY. DESCRIPTION OF PLATE II, Illustrating Mr. G. Norman’s paper on some Undescribed Species of Diatomacez. Fig. 1.—Asterolampra Stella. 2.—Surirella Baldjikit. 3.—Coscinodiscus fuscus. 4.—Nitzschia vitrea. . 5.—Aulacodiscus Sollittianus. 6.—Hupodiscus ovalis. 7.—Navicula bullata. | All magnified 400 diameters. ram Mur hie. Veb INS GL We Bo Be. Bb Sy Dene ptts ae Stet estt ay ee ro TsT, S953 Fs © “oo ec % 6 rr a, Qoore: O88 606% CE 58. A € Ce RES o¢ ¢ OF 9.0 OS O.085 acer Sob oo2e, ACG Eeeegoe CE Evecoo es IM eb OO 1% ro wo eos Soto, Sex ole oe oo eS Hoe, 0 fe Laas 2.02980 P2009 93 223% e545 043% 5 39 904, rid Ob, 06 0n 208 9.02690 © 03089,9 OSrate g 9535 570 025 ° G.N& T.W.del. T.Wese. MI oO WttL ND Se EARL IID Hie Ble ee aPC TIO NRE Ch ef) AIRE Ng ee rc 8 Me 8s * & WA.del. Tuffen West sc. TRANSACTIONS OF MICROSCOPICAL SOCIETY. DESCRIPTION OF PLATE III, Illustrating Mr. Addison’s paper on Changes of Form in the Red Corpuscles of Human Blood. Fig. 1.—Natural forms of the red corpuscles of human blood. 2.—Alkaline forms, produced by saline and alkaline liquids. 3.—Acid forms, produced by the action of weak acid liquids. 4.—Tailed forms, produced by Sherry wine, &. f rae ‘ ws ; ‘ Py i i F pie ‘hg . eel Lib ae, we ‘“ KA RAM z kate : ‘ : ‘ ; ‘ : 2 i i : ' roti 3 Fas oo? So as coll oof 90000097 9900000G0a ° 9 go feKe) ) 9 of8 ie} ° noo 290060000 05 Gdq ° o oF 6 02 fe) USO OF 00 90000 ecog= eco 8909C SesoSce H beset RK Greville del. T.West sc. TRANSACTIONS OF MICROSCOPICAL SOCIETY. DESCRIPTION OF PLATE IV, Illustrating Dr. Greville’s paper on New Diatoms, Series I. Fig. 1.—Stictodiscus Buryanus, focused for the radiating lines. 2.—The same, focused to show the plicate character of the disc. 3.—S. Johnsonianus. 4.—S. insignis, x 600. 5.—Coscinodiscus armatus. 6.—C. tuberculatus. 7.—C. biradiatus. 8.—C. elegantulus. 9.—C. Barbadensis. 10.—Triceratium capitatum. 11.—T. Westianum. 12.—T. Barbadense. 13.—TZ. nitidum. 14.—T. cellulosum. All the figures are X 400, except fig. 4, which is x 600 diameters. The Barbadoes species are described from a fine series of slides supplied by Mr. J. T. Norman. = | | | | | | } | | Hy: | TRANSACTIONS OF MICROSCOPICAL SOCIETY. DESCRIPTION OF PLATE V, Illustrating Richard Beck’s paper on the Metamorphosis of. a Coccus found upon Oranges. Fig. 1.—Female. 2.—Heeg taken from one of the above. 3.—Young Coccus shortly after breaking from the egg. 4,—Male insect at the earliest period at which any traces of sexual charac- ters can be distinguished. 5.—A male insect further advanced. 6 jet as) MALUTE. 7.—Shell of a male Coccus, with indications of its formation at three dis- tinct periods,—the larval covering, the pupal covering, with a subsequent addition for the protection of the wings of the imago. 8.—Mature female removed from the shell. In all the figures where letters are employed, @ represents the upper, b the lower surface. TRANSACTIONS OF MICROSCOPICAL SOCIETY. PLATE VI, Illustrating Dr. Guy’s paper on the Crystals of Arsenious Acid, showing the sublimates as they appear by the monocular and binocular microscope by transmitted and reflected light. a; fig ys N nay Dat \ en West ad we ITC Toff ‘rrr 3 SS S mp .cht sic West 1x W. HE ser) 82 & « rye OSS, fo} 09 Ove Ce O Or A : Ree eave ley 79 9999 ( 23 oa 7929992 as. SAPs: ( aa8 999 OW TRANSACTIONS OF MICROSCOPICAL SOCIETY. DESCRIPTION OF PLATE VIII, Illustrating Dr. Greville’s paper on New Diatoms, Series II. Fig. 1.—Rylandsia biradiata, X 600. 2.— Coscinodiscus symmetricus. 3—5.—Creswellia superba. 6, 7.—uodia Barbadensis. 8.—Triceratium cornutun. 9.—T. productum. 10.—T. inconspicuum, X 800. 11.—TZ. delicatum, xX 600 12.—Z". labyrintheum. 13.—7’. areolatum. 14.—T), tessellatum. 15.—T’. robustum . 16.—Z. Browneanum. 17.—T. (?) blanditum. *18.—Cocconeis Grantiana, x 800. 19.—C. granulifera, X 600. All the figures are X 400 except where the contrary is mentioned. TRANSACTIONS OF MICROSCOPICAL SOCIETY. DESCRIPTION OF PLATE IX, Illustrating Dr. Greville’s paper on New Diatoms, Series III. Fig. 1.—Brighiwellia elaborata. 2, 3.—Triceratium notabilis. 4.—T. microcephalum. 5.—T'. insignis. 6.—T. rotundatum. 7.—T. amcenum. 8.—T. obscurum. 9.—T'. Harrisonianum. 10.—T. giganteum. 1].—Amphitetras minuta. All the figures are X 400 diameters. Fray Mer he TAU NS AE ieee 9 J9 9099S 355o 9 69999999000 § 299900950909 a9 2999 . i x Q ue , é | i 4 * ™ AS Tram Nior Soe Valk NS Fa, ——— O\fo 0 2 9 olloo 2 2 aloo 690 05 eS o 0 gio 6090, OP S0907 CU 0, 06a 98 000 Cons 800g 9 OG 9 dio © 02 90.0 002 00 2 ies OOo? O00000 ij F ik ul R.K.G. del. Tuffen West, sc. ’ W. West, pe TRANSACTIONS OF MICROSCOPICAL SOCIETY. ao DESCRIPTION OF PLATE X, Illustrating Dr. Greville’s paper on New Diatoms, Series LV. Tig. ].—Stictodiscus Californicus. 2,3.—S. Kittonianus, x 600. 4), Coscinodiscus patellefor ints. 0.—Triceratium marginatum, 6.—1'. pulcherrimum. (—9.—T. Abercrombicanum. 10.—Z. tnopinatum. l1L.—TI. approximatum. 12, 13.—T. gratiosum. 14.—T. variegatum. 15.—TZ. nebulosum. 16.—Amphiprova conspicua. All the figures except 2 and 3 are X 400, Errata in Series U1.—Vor Priceratium notabilis and 7. insignis, read 2’. notabile and 7’, insigne. 8 Oa eh NT Pere INDEX VOLUME TO TRANSACTIONS. EX: A. Actinocyclus, Whr., 27. Actinoptychus dives, Khr., 41. Addison, William, on changes of form in the red corpuscles of human blood, 20. Amphiprora, 86. is Conspicua, Grev., 86. Amphitetias, Ehyr., 77. 7 minuta, Grev., 77. Arsenivus acid, William A. Guy, on the microscopic characters of the erystals of, 50. Astrolaumpa stella, Norm., 6. Aulacodiscus Sollittianus, Norm., 7. B Beale, L. 8., on a portable field or clinical microscope, 3. Beck, Richard, on the metamor- phoses of a Coccus found upon oranges, 47, Blood, William Addison, on changes of form in the red corpuscles of human, 20. Brady, H. B., on the seed of Dicty- oloma Peruviana, D. C., 65. Brightwellia, Ralfs., 73. = elaborata, Grev., 73. C. Cocconeis, Khr., 72. » DBrightwellii, Kdw., 26. v3 Grantiana, Grev., 72. : » granulifera, Grev., 72. Coccus, found upon oranges, Richard Beck on the metamorphoses of a, 47. Condenser, for the microscope, J. B. Reade, on a newhemispherical, 59. Coscinodiseus, Ehr., 42, 58, 80. | Coseinodiscus armatus, Grev., 42. FA Barbadensis,Grev., 48. Pe; beradiatus, Grev., 42. as elegantalus, Grev., 42. 9 fuscus, Norm., 7. = gemmifer, Khy., 27. . lime, Khy., 27. 5 patelleformis, Grev., 80). bys symmetricus, Grev., 68. /uberculatus,Grev., 42. Creswellia, Grev., 68. - superba, Grev., 6S. Cylotella rota, Kitz, 40. » rotula, Kitz, 40. D. Diatomacee, George Norman, on some undescribed species of, 5. y mounted by E. Samuels, for the Boston (U.S.) Society of Natural History, and presented to ihe Microscopical Society of London; report on, by Charles Stodder, 25. Diatoms, R. K. Greville, descriptions of new and rare, series I, 39. ” oy) If, 67. ” 9 III, 73. Dictyoloma Peruviana, D. C., H. PB. Brady on the seed of, 65. Discoplea dives, Ehr., 41. - rotula, Khr., 40. % rota, Khy., 40. E. Eccremocarpus scaber, 65. Eupodiscus fulvus, W. Sow., 27. Fi ovalis, Norm., 8. Euodia, 69. » Barbadensis, 69. 090 INDEX TO G. Greville, R. K., descriptions of new and rare diatoms, series I, 39. 33 ” LT 67. ” » IIT, 73. Guy, W. A., on the microscopic characters of the crystals of arsenious acid, 50. i. Lobb, on the self-division of M/zcras- terias denticulata, |. M. Micrasterias denticulata, Lobb on the self-division of, 1. Microscope, James Smith on a dis- secting, 10. 3 F.H. Wenham, on a new compound binocular and single microscope, 15. » Lionel 8. Beale, on a portable field or clinical, 3. Microscopical Society, annual mect- ing of, 29. 35 - auditor’s port, 30. ” ” president’s address, 31. N. Navicola ballata, Norm., 8. Nitzschia Amphiouys, 5. », vitrea, Norm., 7. Norman, George, on some unde- scribed species of Diatomacee, 5. O. Odontidium Baldjickit, Brightw., 5. R. Reade, J. B., on a new hemispherical condenser for the microscope, 59. Rylandsia, Grev. and Ralfs, 67. a biradiata, Grev., 68. 5. Smith, James, on a dissecting micro- scope, 10. Stauroptera aspera, Ehy., 28. Stictodiscus, Grev., 39, 79. y Californicus, Grev., 79. i" Burganus, Grev., 40. is dives, Grev. (sp.), 41. is insignis, Grev., 41. 3 Johnsonianus, 41, | | | re- | TRANSACTIONS. Stictodiscus rota, Grev. (sp.), 40. es votula, Grev. (sp.), 40. Stodder, Charles, report on slides of Diatomacee, mounted by EH. Sam- uels, for the Boston (U.S.) Society of Natural History, and presented to the Microscopical Society of London, 25. Surinella Baldjicku, Norm., 6. Syuedra Hennedyana, Grev., 36. » magna, Kdw., 26. » pacifica, Kdw., 26. » undulata, Greg., 26. ge Triceratium, Khy., 43, 69, 74, 81. “5 Abercrombieanum, Grev., sé aculeatum, Grev., 45. : ameenum, Grev., 75. 2 areolatum, Grev., 71. os Barbadense, Grev., 44. cA blanditum, Grev., 45, 72. = Browneanum, Grev., 72. 4d capitatum, Grev., 43. é cellulosum, Grev., 44. ‘a circulare, Kidw., 26. , cornutum, Grev., 45, 69. a delicatum, Grey., 45, 70. 5 giganteum, 77. nd gratiosum, Grev., 85. és Harvrisonianum, 76. i inconspicuum, Grev., 45, 70, 84. ‘5 Jabyrintheum, Grev., 45, a narginatum, Brightw.,81. i microcephalum, Grev., 74. os nebulosum, Grev., 86. “e notabile, Grev., 74. fe obscurum, Grev., 76. ‘is ornatum, Grev., 45. e insigne, Grev., 75. mh productum, Grev., 45, 69. Ns pulcherrimum, Grev., $1. i robustum, Grev., 71. s rotundatum, Grev., 75. 2 tessellatum, Grev., 71. variegatum, Grev., 85. a undatum, Kdw., 26. es Westianum, Grev., 43. W. Wenham, F. H., ona new compound binocular and single microscope, 15, TRANSACTIONS OF THE MICROSCOPICAL SOCIETY OF LONDON. NEW SERIES. VOLUME X. LONDON: JOHN CHURCHILL, NEW BURLINGTON STREET. 1862. TRANSACTIONS. On the CircuLation in the TADPOLE. By W. U. Warrtney. (Read June 13th, 1861.) 1 nAve been surprised at the comparatively small number among the many who, in the present day, devote a good deal of time to the microscope, who have examined the tadpole. But I am sure that not one among those who have done so will easily forget the sense of surprise and delight felt on first looking through the transparent cabinet of this little creature’s curiosities. He reveals to us, through the eye of the microscope, the greater part of his entire mechanism in living and liveliest operation, the contemplation of which never fails to excite equal astonishment and pleasure. I had often examined the tadpole under the single micro- scope, but on looking at him under the binocular I was aston- ished at the additional grasp, as it were, of vislon—a power of penetration as well as distinctness—given by this instru- ment; and felt convinced that, with this great addition to our means, we might obtam a more complete view of the organism, and of the circulation especially, than had yet been attained. In conjunction with my friend, Mr. Fitzgerald, and with his binocular microscope, I began the series of observations which have produced the accompanying dia- grams, wherein the complete circle of the circulation is represented. As in the best English standard work on comparative physiology (I mean Dr. Carpenter’s)—a work enriched from foreign as well as native sources—there is no such complete representation, we have presumed that the binocular microscope has enabled us to obtain, for the first time, a clear and comprehensive view of the tadpole’s vascular system. Placing the tadpole on his back, we look, as through a pane of glass, mto the chamber of the chest. Before us is the beating heart, a bulbous-looking cavity, formed of the VOL. xX. a 2 Wuirney, on the Circulation in the Tadpole. most delicate, transparent tissues, through which are seen the globules of the blood, perpetually, but alternately, enter- ing by one orifice and leaving it by another. The heart appears to be slung, as it were, between two arms or branches, extending right and left. From these trunks the main arteries arise. The heart is enclosed within an envelope or pericardium. This pericardium is, perhaps, the most deli- cate and is, certainly, the most elegant beauty in the creature’s organism. Its extreme fineness makes it often elude the eye under the single microscope, but under the binocular its form is distinctly revealed. Then it is seen as a canopy or tent, enclosing the heart, but of such extreme tenuity that its folds are really the means by which its exist- ence is recognised. Passing along the course of the great blood-vessels to the right and left of the heart, the eye is arrested by a large, oval body, of a more complicated structure and dazzling appear- ance. This is the lung, which, in the tadpole, is a cavity formed of most delicate, transparent tissue, traversed by certain arteries, and lined by a crimson network of blood- vessels, the interlacing of which, with their rapid currents and dancing globules, form one of the most beautiful and dazzling exhibitions of vitality. The tadpole is hatched with respiratory and circulating organs that resemble those of the fish. It lives in the water, breathes oxygen from the air contained in the water, and during the early period of its existence respires exclusively by gills. Our inquiries do not apply to this the earliest stage of tadpole life, but to the middle and Jater periods, the stage of transition between the fish and the reptile, when, as Dr. Carpenter expresses it, “there is a kind of balancing between the organs which are disappearing and those which are being evolved.” It will be remembered that in the fish the heart has two cavities, an auricle and ventricle; that the blood, returned by the veins of the body to the auricle, passes into the ventricle, and is then transmitted to the gills, where, being exposed to the air contained in the water, it becomes deprived of carbonic acid, aerated, and rendered fit for re-circulation through the system. In the reptile we find a modification of plan coincident with the lower tone of vitality which distinguishes these cold-blooded creatures. Their heart has three cavities, two auricles and one ventricle; and by this contrivance there is a perpetual mixture in the heart of the impure carbonized blood which has already circulated through the body, and flows into the ventricle from the right auricle, Wurrnny, on the Circulation in the Tadpole. 3 with the pure, aerated blood returned from the lungs, and which also flows at the same instant into the ventricle from the /eft auricle. Thus the habitual circulation of this “ cold- blooded ” mixture is the cause of the low tone of vitality that distinguishes the perfect reptile. We now arrive at the consideration of the tadpole, who, during the middle and latter stages of its metamorphosis, assumes a condition which is neither that of fish or reptile, but something which differs considerably from both. For the purpose of observation the tadpole must, of course, be selected during the period in which the skin is perfectly transparent. ‘The first examinations revealed plainly enough the appearances already described of the form and situation of the heart, and the three great arterial trunks proceeding (right and left) from it. The course and destination of these were not so easily arrived at. Many observations were required, on tadpoles of various sizes and carefully prepared, to arrive at what I believe to be the true anatomical and physiological arrangement of these vessels. First, all these are closely connected with the corresponding lung. The upper one (the cephalic) runs along the upper edge of the lung, and gives off, in its course, a branch which ascends to the mouth, and is mainly distributed to the thick-fringed lip which surrounds the mouth, and is evidently an organ of sense, playing the part of judge and sentinel to this important entrance. It is profusely supplied with blood by this artery, and the blood is returned by a corresponding vein. We may call these the /adzal artery and vein. The cephalic artery continues its course around the lung (forming, to all appear- ance, the edge of that organ), until it suddenly curves upwards and backwards, and reaches the upper surface of the head, where it dips between the eye and the brain, towards which it is evidently travellmg. We may now call it the cerebral artery. Dr. Carpenter speaks of the second main trunk as con- tributing with the third to form the great systemic aorta, which descends into the abdomen. The evidence we obtained appears to be at issue with this statement. To us the micro- scope revealed the course and distribution of this artery through the lung, freely communicating, by a network of vessels, with the upper or cephalic branch, and with the lower one, which I am next to describe. This middle one, therefore, would seem to be the true pulmonary artery. The third main trunk (which we have been at great pains to trace) clearly enters the lung, distributes branches, but con- finues its course as a large trunk, bending downwards to the 4 Wurtney, on the Circulation in the Tadpole. lower surface or floor of the lung, whence it emerges, curving towards the spine, and becomes, as I shall presently show, the great abdominal aorta. If these statements are correct, they exhibit a different vascular arrangement to that which has hitherto been represented, and they have an important bearing upon certain physiological points presently to be mentioned. I will now speak of the means by which we were enabled to trace the existence and course of blood-vessels ordinarily invisible. It would be a mistake to suppose that you can make out distinctly, in the average of tadpoles taken, with- out preparation, and placed under the glass, the plan of the blood-vessels, even as far as I have yet described them. The great obstacle is the large coil of intestines, usually distended with dark-coloured food, undergoing digestion and travelling along the bowels. This, of course, effectually screens every thing behind it from the eye of the observer. Moreover, by distension the bowels stretch upwards to the chest, reaching the apex of the heart, and often concealing a part of the lungs. To empty the bowels, therefore, was the great de- sideratum. I immersed tadpoles in solutions of many of the known aperient drugs—Epsom salts, colocynth, aloes, ela- terlum, &c., but no purgative effect was produced. But as the contents of the bowels are, in the natural state, per- petually passing away, I thought that by giving them an opportunity of clearing themselves, and at the same time preventing an accumulation of fresh matter by putting the tadpoles upon low diet, we should extend our field of vision. This experiment succeeded. The tadpoles lived on plain water for some days; much of the intestinal contents passed away, the canal became comparatively, though not entirely, empty, and the bowels, shrinking in proportion, occupied a smaller space. | Figure 1 (Pl. I) exhibits what we see ordinarily when a tadpole is looked at—heart, the main arterial trunks, and the greater part of both lungs. But under the mfiuence of low diet we gain a much clearer and more extended view of the vascular system. Water diet, of course, impoverishes the blood, which is rendered paler, as well as reduced in quantity. This effect upon the lungs increases their trans- parency, and by diminishing the quantity and redness of the blood in the minute vessels, lessens the dazzling, dancing movement of red globules, which, most beautiful to look at, is yet perplexing to the eye in its endeavour to catch dis- tinctly and trace the course of the three large arteries which, I have said, traverse these organs. But in proportion as the Wurtnery, on the Circulation in the Tadpole. 5 minute branches and their contents are Jess conspicuous, the large trunks become traceable ; and we have repeatedly been able to follow their course as they have lain naked and un- encumbered beneath the eye (see figures). The bearing of this in a physiological point of view I shall reserve till we have completed the circle of the vascular system. Figure 2 exhibits the more extended view of the vessels obtained under the infiuence of low diet. Here are vessels revealed which, till now, were invisible. But we will continue our course along the arteries. The third trunk, traversing the lung, is now seen to emerge from its lower edge or floor, and descends into the abdomen. There could be no doubt that this contributed to form the great ab- dominal aorta, conveying the blood which supplies the bowels and all the abdominal organs. Still it was partially hidden. We had not yet seen the vessel on each side descend and unite with its fellow to form the abdominal trunk. But this desideratum was at last vouchsafed to us in a most unex- pected manner. It happened that on one occasion a small, black-looking little fellow was put under the microscope. He was taken from a jar of fresh tadpoles who had been regaling upon green weeds. To all appearance opaque, he proved, to our astonishment, transparent from head to tail! He was an animated case, and nothing more. His heart was beating and his blood circulating, but the latter was quite colourless, not a single red globule was visible anywhere. The creature was a mass of outlines merely. The globules chased one another like globules of water, the heart was a colourless globe, the lungs were two transparent ovals, and the bowels a colourless, empty, transparent coil. Our animated case, however, proved to be “a case in point.” That which we had long been searching for was now before us. Through the empty coil we saw the artery on each side descending from the lungs, converging to the spine, meeting its fellow, and with it uniting to form the abdominal aorta (fig. 3). After the aorta has supplied the abdominal viscera, we find a prolonga- tion, or caudal artery, descending to the tail, the all-impor- tant organ of locomotion in the tadpole. This artery, entering the root of the tail, is imbedded deeply in the flesh, whence it emerges, and then continues its course, closely accompanied by the vein, to within a short distance of the tail’s extremity, where, being reduced to a state of extreme fineness, it terminates in a capillary loop, which is composed of the end of the artery and the beginning of the vem. The artery, in its course, gives off branches con- tinually to supply the neighbouring tissue. You may often G Wuitney, on the Circulation in the Tadpole. observe that the blood-current in the tail, even in the main artery or vein, is sluggish or even still. This occurs inde- pendently of the heart, which may continue to beat as usual; and it happens, because the circulation in the tail depends very much on the motion of the organ. When this is suspended (as in confining the tadpole under the micro- scope), the blood moves sluggishly, or stops, till the tail regains its freedom and motion, when the activity of the current is restored. This principle is thus alluded to by Dr. Grant :—‘‘It is the restless activity of the worm and of the insect that makes every fibre of their body, as it were, a heart to propel their blood and circulate their fluids, while the slow- creeping snail that feeds upon the turf has a heart as com- plicated as that of the red-blooded, vertebrated fish, that bounds with such velocity through the deep. It is because the fish is muscular and active in every point that it requires no more heart than a snail to keep up the necessary move- ments of its blood.” Having arrived at the end of the arterial system, which conveys the blood from the heart to the extremities, we will now trace its return by the veins back again to the heart. The caudal vein runs near to the artery during the greater part of its course, with its stream, of course, towards the heart. This stream is swollen by perpetual tributaries flowing into it at all points of its course, from vessels so numerous that their loops form a network which covers the entire surface of the tail. As the vein approaches the root of the tail it lies superficial to the artery, and diverges from it at the point of entering the abdomen. UHere it approaches the kidney, sends off a branch which encloses that organ on the one side, while the main trunk continues its course on the other, re- ceiving tributaries from the kidney as it passes. By this time this vein has become the chief river of venous blood, the vena cava inferior. Passing upwards behind a coil of intes- tine, it approaches the liver, and runs in a curved course along the margin of that organ, where it receives the large residue of the blood from which the Jdz/e has been secreted. This blood is seen to enter the vena cava by numerous fine channels, which converge towards the great vein as it passes in close proximity to the organ (figs. 2,3). Beyond the liver the vena cava continues its course upwards and inwards to its terminus in the sinus venosus or rudimentary auricle of the heart. This terminus is the junction of not less than six distinct venous trunks, incessantly pouring their blood into the heart. Figure 2 illustrates that the junction of these venous trunks, and, in part, the vessels themselves were revealed under the influence of the low-diet system Wuirtney, on the Circulation in the Tadpole. a We have already traced the lower vena cava to the sinus venosus. Let us now return to the head, where we left the cephalic arteries to supply the brain, lips, &c. The circula- tion in the fringed lips forms a most complicated network of vessels, out of which proceeds a vein corresponding to the artery already traced. ‘This descends in a direct course till it joins the principal vein of the head, which corresponds to our own jugular. This latter, formed by the union of smaller ones converging to it from all parts of the head, descends in front of the large transverse muscles, passes downwards in front of the lung close to its inner edge, and continuing to descend in a direct course, seems to be making its way into the abdomen. But the abstinent system, by removing the screen of loaded bowel, revealed the subsequent course of this vessel. The vein, having reached the lower edge of the lung and arrived at the very margin of the abdomen, turns suddenly at a right angle and runs straight to the sinus venosus. We observe that at the poimt of the angle this vein receives into it the current of another large one, running upwards from the abdomen to meet it. Herein is the probable explanation of this eccentric course (figs. 2, 3, letter vr). The union of this jugular vein from above with the abdominal vein from below forms the upper vena cava. We have two more large abdominal veins, which meet close together, and pour their blood into the sinus venosus, between the lower vena cava on one side and the upper vena on the other (vu). We have detected distinctly on the right side a venous trunk, returning bleod from the lung, and emptying itself into the auricle or sinus (v). This is the pulmonary vei, bringing the aerated blood from the lung to the heart ; but observe that the proportion of aerated blood thus contributed is very small compared with the quantity of venous blood poured into the same cavity at the same moment from the five other sources I have described. There is doubt- less a left pulmonary vein, corresponding to the one on the right side, but as we have not yet been fortunate enough to see it, I have not figured it. Thus we have traced the blood through its main channels and completed the circle of its course. But the special point in relation to the anatomy and physiology of the tadpole, as a creature distinct from the fish on one hand and the reptile on the other, yet remains to be mentioned. The ¢hree large arteries which arise from the heart become (according to the evidence we have obtained, the cephalic, pulmonary, and aortic trunks. Herein we differ from the received view of these arterial arrangements. The first trunk, according to Dr. Car- 8 Warner, on the Circulation in the Tadpole. penter (and as we have also observed) is devoted to the head ; but Dr. Carpenter does not mention any connexion between this vessel and the lung. Now, this cephalic artery, as it travels over and rests upon the upper surface of the lung, receives into it small branches from the subdivisions of the pulmonary artery,sothat there is a direct communication between these two | vessels. The second and third trunks, according to the same authority, form the aorta, the current fiowing continuously from the heart into the abdomen; while a fourth trunk is mentioned by Dr. Carpenter as the pulmonary artery, devoted exclusively to the lungs. But our own observations have convinced us that it is the second trunk which enters and is distributed through the lung as the true pulmonary artery, while the third trunk also enters and passes through the lung, inosculating, in its course, with branches of the pulmonary artery, and then emerges from the floor of the lung to enter the abdomen, and with its fellow form the aorta or great systemic trunk. With regard to the fourth vessel, which Dr. Carpenter calls the pulmonary, we have never been able to discover such a one. Now, according to Dr. Carpenter’s view, it is clear that the blood in the cephalic arteries, and the blood descending to the aortic trunk in the abdomen, is the mixed arterial and venous blood expelled from the heart, in short, the blood of a reptile. But the habitudes of the tadpole are not those of the reptile. He exhibits all the activity and liveliness of the fish long after the gills (the characteristics of his fish life) ave supplanted by the developing lungs. Activity characterises every function in the tadpole at this period. In this respect he presents a contrast to the frog, which cannot fail to strike the most careless observer. The functions of nutrition, growth, development, and locomotion, which constitute the great business of his life, are all habitually and vigorously performing. For these functions, and for this activity, a constant supply of pure, aerated blood is known to be essential. On the other hand the circulation of mixed venous and arterial blood in the frog is consistent with the lethargy, imertness, coldness, low vitality of the creature. Dr. Carpenter observes, “the correspondence between the general vital energy in any 1n- dividual system, and the activity of respiration, must be evident to the observer ;” and quotes for example “ the energy of respiration in the active and rapacious eagle as compared with the timid and indolent tortoise.” I think we may paraphrase this passage by comparing “ the active and rapacious tadpole” with the timid and indolent frog.” The activity of the tadpole is unquestionable. As for his ra- Burton, on a Portable Revolving Table. 9 pacity, I know him to be a cannibal. A large tadpole, and especially if he be hungry, will kill and devour his smaller brethren ; while the body of a dead tadpole put into a jar of living ones is attacked in a moment, and greedily consumed as a bonne bouche of the highest order. These ferocious qualities are not found in the frog. Again, Dr. Carpenter observes, “‘ The development of the locomotive powers, which may be regarded as an indication of the general activity of the organic functions, will be found peculiarly connected with that of respiration.”” Now, in the tadpole we have the development, first, of the tail, an active and vigorous organ of locomotion, and which is often large enough to make a winding sheet for the whole body; and, secondly, the development of the four extremities, the locomotives of the future frog, which business is completed during the tadpole state. | Thus there seems to be plenty of evidence that some pro- vision exists in the tadpole for a much higher aeration of the blood than the mere reptile arrangement will permit. And I submit that if we have been able to trace each of the three great arterial trunks into immediate connexion with the lungs themselves—the cephalic running over, or rather form- ing, the upper edge of the lung, and directly receiving blood from branches of the pulmonary artery; the pulmonary, dis- tributed to the lung itself; and the aortic, also penetrating the chamber of the lung to imosculate with, and receive blood from, the pulmonary—then we have discovered this pro- vision, and have found an adequate explanation for all those active vital phenomena in the tadpole which appear to indi- cate a very complete aeration of the blood. On a PortaBLE REVOLVING TABLE. By Joun Burton, Esq. (Read Oct. 9th, 1861.) A communication of Mr. Jansen in the Journal for July suggested to me the desirableness of laying before the Society a portable revolving table which I had recently con- structed for my own use. Where only one microscope is used, an apparatus to move 10 Burron, on a Portable Revolving Table. upon an ordinary table has the advantage of enabling the exhibitor to have various things lying at hand, while the microscope is being passed round to others. In constructing this my object was to have a table _ efficient, at the same time small and light, one which might conveniently accompany the microscope even on visits into the country. Care was taken to have the space needed for a first-class instrument, and lamp, with bull’s-eye and side condenser; securing this, there is space for everything else. The upper part is in five sections, tapering from 32 inches to a point, of deal + inch thick, made strong by having American leather-cloth glued on the upper and coloured cotton on the under surface, both being arranged to allow the parts to fold up like a fan. This rests on a triangular frame of 19 inches, made of light, tough wood, % inch deep by + inch, with one bar across the middle. This bar is joined to the sides by two small pins at each end. The sides are united by a joint similar to that of a carpenter’s rule, but made of simple plates of brass, one above, one under- neath, as shown in Diagram 2. In the under one is a hole for the pivot, on which the table rests and revolves. The other angles are mortised, and held together by one of the two wires which give support to wheel-rollers. These wheels (about 1+. inch diameter) are somewhat tapered, to move more smoothly in a circle, and are covered with cloth. The pivot, a small wire, is fixed in a turned base. This being placed in the middle of a round table, or near the end of a dining table, and the pivot-hole passed over, the whole is moved easily round, without damage to wood-polish or cloth, and its circular action preventing its running off the table. Diagram 1 shows the table as in use. t. cr arena Cttédttttttttsdszzmz mmr: Tf Luau Beck, on the Universal Achromatic Microscope. ae Diagram 2 the table turned over, the “ upper part” folded as a fan; one wheel taken out, and its corner disjointed ; the middle bar, with its connecting wires. The dotted lines mark the holes to which each wire of the wheel and centre pivot belongs. A Description of the UNiversat AcHRomatic Microscope, as contrived and manufactured by Smitu, Beck, and Beck. (Read Oct. 9th, 1861.) Tue word cheap, when applied to the achromatic micro- scope, by no means loses its varied and comprehensive mean- ing. As manufacturers, we are not unfrequently told by the gentleman who has paid his hundred guineas for his in- strument that he does not consider it expensive, but cheap, compared with the imstruction and amusement it affords, or, indeed, as nothing, when contrasted with an indulgence in many other tastes; whereas, on the other hand, we receive a letter from an inquirer for a cheap microscope, in which, after stating its numerous qualifications, we are told we must on no account exceed the sum of 10s. 6d. Now, disregarding these extremes as well as “the happy medium” (for our price is much nearer the smaller sum), we still claim the title of cheap for the microscope which is represented in Plates V and VI. At first sight, the instrument undoubtedly appears one- sided, and to those who are inclined to form an opinion as to its deformity, we must confess that, after a most careful 12 Beck, on the Universal Achromatic Microscope. consideration of the whole as well as each individual part, we have in no instance made a sacrifice of efficiency for the sake of appearance ; but with this expression of our motive, we would also ask the casual observer to withhold his judgment until the working qualities and the price of the instrument are also before him. The foundation of the stand is a large, circular base (a), and near its circumference, on the left-hand side, is a strong pillar (B); at its top is the axis upon which the remainder of the instrument turns, and with so equal a balance as never to require more than a slight screwing down of the small, milled head (c) to secure any particular position. On the same centre as the axis is a large, milled head (pn), by which a quick motion is given to the body (2), and depend- ing from the smaller part of the same milled head is a lever () ; this of itself hangs free, but when held at the end and pressed sideways, either nearer or further from the pillar, it obtains a gripe upon the milled head (p), which can then be turned so slowly as to constitute a very good slow motion.* The quick-motion milled head and the slow-motion lever are always in the same position, and do not alter with any in- clination of the body they are also so low down; that in using them, the hands are very little raised from the table ; this latter advantage also appliesto the stage (a) which is screwed on at the lower end of the limb (e) at less than four inches from the bottom of the stand. On the top of the stage is a double spring (1), branching right and left over a brass plate (k). On this there is a ledge (x) for the object to rest upon, and in continuation, on the right-hand side the plate, is bent over, so that it may be firmly grasped by the fore and middle figures underneath and by the thumb above. By this arrangement the object can be moved freely in every direction, and will retain its position after the hand is withdrawn. If necessary, the short spring (a) may be used when the object has to be held firmly on the plate. The small pin (v) is for holding the forceps (0). Beneath the stage is a cylindrical fitting p, for all the appa- ratus required in that position. The diaphragm (Q) is, however, made a fixture to the mirror-stem (R), except thatit will turn away entirely on the left side when necessary; it is provided with one small aperture (x) for the lower powers, and this can be closed, or otherwise by a small shutter (x). A concave mirror (s) swings in a rotating semicircle (Tt), which * Mr. Brookes was, we believe, the first to recommend this kind of slow motion, and the chain motion; and the chain movement, which we have also adopted, has hitherto been chiefly confined to Mr. Lobb’s instruments. Beck, on the Universal Achromatic Microscope. 13 is attached to an outside sliding or tube, the inner tube being screwed beneath the stage, and almost opposite a side con- denser (v) is fixed for the illumination of opaque objects ; itis provided with ball-and-socket joints, which afford any neces- sary movement, and also the means of turning it out of the way when not in use. The object-glasses are two in number, one inch, and a quarter inch focus, and of the respective apertures of 20 and 75 degrees; these, when combined with the two eyepieces give the four linear powers of 60, 90, 240, 360; the higher power has no adjustment for variations in the thin glass or other media when interposed between its front lens and the object, but it is corrected for a piece of glass ‘008 thick, and for objects covered with glass of such measurement its definition will be best. The eye-pieces are small in diameter, but are of a construc- tion (we believe introduced by Kelner) which gives a flat, and for their size a large, field of view. Their chief fault will, we believe, prove a general advantage; any dust or moisture upon the field-lens is so annoyingly apparent, from its bemg in the focus of the eye-lens, that those: who use this form will be compelled to wipe the lenses frequently ; and not only this, but they will soon learn the necessity for the constant examination and the occasional cleaning of every surface of glass that they have about their micro- scopes. With merely enumerating a pair of forceps (0), asmall pair of pliers (v), a glass plate, with a ledge (w), and an upright ma- hogany case, we sum up the achromatic microscope we shall supply for five guineas. Although, up to this pomt, the mstrument may be consi- dered as complete and probably sufficient for many ob- servers, yet we are quite sure, if any one who possessed such a stand were to find that, as his interest in microscopi¢ re- search increased, he were unable tomake additions to the power and to the capabilities of his instrument, the investment even of five guineas would become a source of regret or a check, perhaps to his enterprise, whilst no credit would be due to the manufacturer. We hope, however, to obtain the most opposite results from the following additions, which can be made to those parts we have already described. In the first place a lower, an intermediate, or a higher magnifying power than those mentioned may be obtained by the addition of a 2in., + in., or 1 in., the respective angles of aperture of which are 9, 45, and 85 degrees, and their mag- nifying powers with the two eyepieces mentioned 30, 45, 14 Buck, on the Universal Achromatic Microscope. 120, 180, 480, and 720 ; besides these, a third eyepiece may be added, which will as nearly as possible double the power of the first. That which we believe our customers will first selves of is a body as shown in Pl. VI, fig. 1; this is so combined as that three object-glasses and three eyepieces shall be attached to it. Only one of each of these can be central with the axis of the body at the same time; but any of the others can be brought into their proper position by pressing in the rounded head of a pin, (8), when either of the discs, (c), can be turned in the required direction, and will be stopped again by the pin, (s), springing out. This will be a great advantage to those who are deterred from making a casual use of the microscope by the trouble first of all, of putting the instrument up, and, secondly, the delays which are caused by the necessary changes ; whilst it will considerably assist in the investigation of objects which are undergoing a change, either in their position or their structure, and when a great range of power is required with the least delay possible. As a luxury, it will apply to every use of the microscope. These remarks apply more especially to the change of the object-glasses; in some cases the eyepieces are to a slight extent in the way, as in using a camera lucida, whilst they are always more or less likely to be condensers of the breath ; and as their change can be made rapidly, we have for these reasons, combined with a complicated structure that was involved, omitted them in the binocular edition. (Fig. 2.) From the very first glance through Mr. Wenham’s last binocular arrangement we have always been convinced, not only that this improvement was essential, but also that it must become universal. We have no cause, more than any other opticians, to urge the necessity of stereoscopic vision im nearly if not all microscopic investigations ; and by bring- ing before you this evening a plan by which we hope to reduce the price considerably, we cast in but a very small mite compared with the liberality of the inventor, who, refusing the least emolument, has presented you with his scheme unpatented. Pl. VI, fig. 2, shows the double body, and it possesses the following advantages :—the object-glasses are mounted on a rotating disc, as already described; an adjustment for different distances between the eyes is made by sliding the draw tubes () up or down, the milled head (r) clamping them im any required position. The reflecting prism is placed close behind the back lens of each object-glass, and with Beck, on the Universal Achromatic Microscope. 15 this arrangement the field of view is not cut off when the objects are viewed as transparent with the highest power. If the single body only be required, the prism can be pushed back by the small, milled head (Gc); or when this is unscrewed, it can be taken out altogether, for the purpose of being wiped. We may here mention that the manufacture of this instru- ment is so arranged as that the change from the square body (Pl. V) to the binocular or other body (Pl. VI) can be made by any one, and with great facility ; so that to add these, or any other parts which are alluded to in this paper, it will not be necessary for the microscope to go into the hands of the manufacturers, or of any skilled workman. As to the necessity for the next addition, there may be different opinions. We have not previously stated that the spring (Pl. V) which holds down the stage-plate (k) can be removed by unscrewing; after this is done the stage is perfectly clear, and any large object, or a small saucer or dish, can be placed upon it. It will also then receive what is commonly called a stage with actions (Pl. VI, fig. 3); this is contrived so to fit on asto admit of its being turned round as a whole, and consequently always central with the body; or, in other words, during the rotation the object will not move out of the field of view; the amount of movement at right angles is half an inch each way, and is effected by means of the milled heads (1, x) ; the object can be moved to and fro on the ledge (1) which also slides up and down, and a small spring can be turned to clamp the object when necessary. The following extra pieces of apparatus can also be added; but as they require no description here, we merely enumerate them to give some idea of the capability of this form of stand: Polarizing apparatus, consisting of two Nicol’s prisms and plate of selenite. Wenham’s parabolic reflector, for dark field illumina- tion. A dark well; and Lieberkuhn’s to the 1-inch and +4-inch object-glasses, for additional opaque illumination. Wollaston’s camera lucida, by which, with the aid of a stage micrometer, any drawing or measurement can be made. A small live box, and a glass trough. At the conclusion of this description (for the length of which we must apologise), whilst not contending for one moment that the performance of this microscope will equal that of our first-class instruments, we are sure it will most satisfactorily exhibit nine tenths of the microscopic researches 16 Beck, on a Coccus upon a Rosebush. already recorded, and we as confidently predict its efficiency for a larger proportion of those observations which have yet to be made in that immense field of nature still un- explored. | — On a Coccus upon a Rosepusu. By Ricwarp Beck. (Read Nov. 13th, 1861.) In a note appended to my former paper on a coccus found upon oranges, and published in the ‘ Microscopical Journal ’ for July, 1861, 1 mentioned that the same insect was very numerous in our own gardens, and at that time my attention was directed to a plant of Cotoneaster against a south wall, which in many parts was literally covered with a female coc- cus of the same species as that already alluded to (Pl. IV, fig. 1). The search for any males seemed, however, quite hopeless, when Mr. Cooke, the optician, of York, having written to me for some of the large garden spiders which he says are not to be found in his neighbourhood, I was hunting on a north wall, and could not but notice a Coccus in great abundance on the older stems of a rosebush, both the male and female insects being visible to the naked eye (fig. 2). For many reasons I for some time believed this to be a species entirely different from that on the orange; the external ap- pearance of all the shields was very different, and when these were turned over the females were so much larger at the head as to be quite different in shape, and of a much darker colour (fig. 3). The eggs, also of a darker colour, were laid in a more or less circular position, and most of the males contained a fly entirely different from that I had previously described. But these were the only differences, and ultimately, after a very careful examination, I traced both males and females, the former more especially, through exactly the same metaphorsoses as I have described in my former paper. The small fly I have alluded to as being present in some of the male shields, and, as I found afterwards, in those of the female also is a species of ichneumon (fig. 4), but its presence alters the external character of the Coccus very little, a slight enlargement in the males only being visible (fig. 5). Beneath the shields there are, however, considerable differ- ences; in the female Coccus the mere fact of a fly bemg de- veloped is sufficient to indicate an unnatural state, and Brick, on the Viscid Lines in a Spider’s Web. Ly whereas the male Coccus, when in its pupa state, undergoes considerable changes in its form, the smooth, hard shell in which the ichneumon fly is developed is invariably uniform ; this shell is left behind when the imago escapes, in the male coccus one or other extremity being removed (fig. 6), but in the female a clean, round hole is made through both shell and shield (fig. 7). From the examination of some skins of Aphides, from which the ichneumon flies have escaped, I believe that in making the hole this portion of the shield is not destroyed, but a piece is cut out which has very much the appearance of the cover of a ‘“ man-hole ” to a boiler. The external features of the ichneumon are also of a much higher class than those of the Coccus. The head is perfect in all its parts ; there are four wings; the eyes are compound ; the extremity of each leg is provided with a beautiful, trum- pet-shaped sucker, and the ovipositor is capable of being protruded or otherwise. To sum up these few and very short remarks, | venture to repeat the two facts which I consider of most interest—first, that the male of this Coccus may under some circum- stances be detected 1 our own gardens; second, that the same species may differ very considerably, more especially on the exterior of the shield, according to the climate, its posi- tion, or the nature of its food. On the Viscip Lines in a@ SpipeR’s Wes. By Ricuarp Beck. (Read Noy. 13th, 1861.) As I have, although very casually, alluded 1m this paper to the large garden spiders, I may, perhaps, be allowed to mention a fact connected with them which came under my notice about the same time. It is well known that in allthe geometric spider webs the concentric lines, with the exception of those in the very centre, are most beautifully dotted with a viscid substance, to aid in the capture of insects. Mr. Blackwall has, I believe, computed that there are more than 100,000 of these gummy drops in a web which is made in about half an hour ; it has always, therefore, been a puzzle in my own mind how this part of the process was effected, and as I had been unable to find any one who could give me a satisfactory ex- VOL. X. b 18 GREVILLE, 07 New Diatoms. planation, I thought I would carefully watch a spider during the operation, when, with only a pocket lens, I could dis- tinetly see that the viscid lines, as first drawn from the abdomen were not dotted. On a careful examination with a microscope, which I took into the garden, the thread at first appeared only slightly thicker than an ungummed line, but after a very short time undula- tions appeared, and subsequently, at the most regular dis- tances, the viscid matter formed into alternating large and small globules. The whole process is such a beautiful illustration of molecu- lar attraction, which Mr. Rainey has been so patiently and profoundly working out with regard to the highest organic structures, that I thought this simple example might interest some of our members. The cold weather has, of course, driven away these spiders till next autumn, at least, but the same result can easily be obtained artificially. Descriptions of New and Rare Diatoms. Serizs V. By R. K. Greviris, LL.D., F.R.S.E., &c. (Read Dec. 11th, 1861.) Havine recently been presented by my friend, Dr. Macrae, Presidency Surgeon, Calcutta, with a considerable series of slides of diatoms collected in Ceylon and on other parts of the Indian coast, I hasten to lay before the Society a notice of some of the more interesting species contained in them. f have not, however, exhausted the materials so kindly placed in my hands, and must reserve a description of other novelties, as well as any general observations [ may have to make on the entire collection, for a future communication. Dr. Macrae has returned to India with the intention of taking every opportunity of prosecuting his diatomical researches, and we may confidently anticipate many interesting dis- coveries in a field comparatively unexplored. SURIRELLA. Surirella fastuosa, Ehr.—HElliptic, with rounded ends, and rather distant coste, dilated towards the margin; median space more or less lanceolate, enclosed within a line of ex- tremely short transverse strie. Length ‘0025 to °0074”. (Pl. £1T, fig. 1.) | ; % (FREVILLE, on New Diatoms. 19 No correct representation of this fine species having hitherto been published, I have been induced to figure a frustule of extraordinary dimensions found by Dr. Macrae in Ceylon. When Professor Smith wrote the first volume of his ‘Synopsis of the British Diatomacez,’ it was considered so rare that some of the slides distributed by him contained only a solitary carefully marked specimen. The figure engraved in the synopsis is Incorrect in outline and deficient in details. Doubtless, however, examples must have occurred to the author of an ovate form, and such a one must have been placed before the engraver ; but Mr. Ralfs remarks (‘ Pritch. Inf.’), “ we have never seen it ovate as described by Professor Smith ;” and I may add my own testimony to the same effect, after having examined a multitude of frustules. The ordinary form is unquestionably elliptic, with rounded ends, as stated by Ralfs, occasionally tending to orbicular, as in the specimen now figured. An error seems also to have been entertained with regard to the structure of the centre of the disc. Smith does not refer to any striation whatever of what he calls the median line, and the figure in the synopsis has the centre wholly blank. On the other hand, the median space is de- scribed in ‘ Pritchard’s Infusoria’ as transversely striated, a character I have been unable to perceive. After making the drawing of the gigantic individual received from Dr. Macrae, Tt examined an extensive series of frustules from British stations, relative to the structure of this part, as well as a slide from Professor Smith himself, and find them all to agree in essential points. It will be seen, by consulting my figure, that the median space is enclosed by a narrow line of exceed- ingly short strie, within which the coste are continued towards a sort of indefinite median line, indicated by the ter- mination of the cost rather than by any genuine line. The normal shape of the median space is correctly described by Mr. Ralfs as lanceolate ; but it varies exceedingly, and I have seen frustules in the same slide exhibiting every gradation from a strictiy linear to a broadly lanceolate median space. In the former case the narrow, striated lines become parallel, aud no room is found for any continuation of the costz. In no instance, however, so far as I have seen, do the strie really cross the median space. In proportion as the striated lines expand, continuations of the costez are introduced, at first with great irregularity, being short, often pointing in different directions, frequently passing across the middle, and scarcely appearing to be connected with the costz at all. As the median space increases, they become more regular, and in largely developed frustules, as in the figure now given, there 20 GREVILLE, on New Diatoms. can be no doubt about their true nature. Besides the proper continuations, there are sometimes short, supplementary ones, which do not answer to any of those exterior to the median space, as well as lines of puncta (see the figure) which must be regarded as abortive supplementary coste. The late Professor Gregory had observed, as he believed, inter- mediate states between this species and S. lata. Such speci- mens have not occurred to myself. I may mention, however, that the structure of the middle portion of the disc is very similar in both species. Nothing definite is conveyed by the figure of S. data in Smith’s synopsis with reference to this part. The median space in that species, as well as in S. fastuosa, is not itself striated, but is bounded on each side by a line of exceedingly short striz, which apparently form a narrow ridge. A differeuce, however, exists in the shape of the median space; the normal form of that of S. /eta bemg linear, or, at least, having parallel sides, while that of S. fastuosa is lanceolate. And although in the latter it not unfrequently becomes linear, I have never seen it expand into lanceolate in the former. In both species, when the median space is narrow, there are no central continuations of the coste, but when the space is broad these occur in S. lata as well as in S. fastuosa. Surirella Macraeana, un. sp., Grev.—-Oblong, constricted in the middle, with broadly rounded ends and narrow median area, enclosed within two lines of punctiform striz; coste distant, externally dilated, the dilated portion transversely punctate. ‘hength 50072 in.4Ph ii fest flab. Ceylon, Dr. Macrae. A very remarkable diatom, distinguished pre-eminently by having the dilated portion of the cost coarsely punctate. At first sight they appear to be transversely barred, but careful adjustment brings out the transverse puncta. The general outline of the frustule resembles that of S. lata, as figured in the ‘Synopsis of the British Diatomacee.’ The lines which enclose the narrow median space are composed of what should be considered normally striz, but these are exceedingly short, and often nothing more than puncta. CAMPYLODISCUS. Campylodiscus biangulaius, n. sp., Grey.—Dise nearly circular, with a broadly linear, smooth, median space, ex- tending at each end nearly to the margin; surface waved so as to produce an angular, converging line between the median GREVILLE, on New Dialoms. 21 space and the margin, and again bent back near the margin at each end; costz rather distant, 4 in ‘001’. Diameter 0036”. (PI. ITI, fig. 2.) Hab. Ceylon, Dr. Macrae. This species belongs to the second section of Ralfs’ first divi- sion (‘ Pritch. Infus.,’ 1861), and is clearly different from any one there described. In the remarkable undulation of the surface of the disc, it is nearly allied to Gregory’s C. angu- laris. By the first bending, a line or ridge is produced on each side, which extends in a curve from one end of the median space to the other. The second bending of the disc becomes most evident towards the ends, where the edge is bent back as in C. angularis. The cost are given off from the median line at right angles, throughout its whole length, and the latter is remarkably clearly defined. In all the specimens I have seen there is a tendency in a number of the central costz to become forked at the margin, but as the apices again unite, it would be more correct to say that they formed little loops. The whole frustule has a very diapha- nous and brilliant appearance, with the markings sharply defined. Dictryopyxis (Hhr.), Grev. Frustules two-valved, cellulose, cohering by simple, more or less convex, junction-surfaces, mto a filament. Valves cup-like, destitute of any silicious connecting band. In consequence of the discovery by the Rev. R. Cresswell of the diatom which now bears the name of Creswellia turris, Professor Walker-Arnott and myself were enabled to define with some precision a little group of Pyw#xidicule, which Ehrenberg had partially indicated, but, from want of perfect materials, had leftin great obscurity. Of his genus Stephano- pyxis, no two of the four species referred to it appear certainly to agree generically with each other; and as his character was drawn up in ignorance of the pcrfect state of any of them, and as, besides, it was not known which of them was to be regarded as the type, we adopted what seemed, under the circumstances, to be the most satisfactory course, and constituted the genus Creswellia upon good and perfect specimens. Three other species have been subse- quently added by myself, and my friend, Mr. Ralfs (who sustains Ehrenberg’s name), mentions under Sfephanopysxis diadema (‘ Prit. Infus., 4th edit., p. 826) that he has seen two frustules connected by the coronal spines. -It con- sequently, without doubt, belongs to the same group. 22 (CREVILLE, on New Diatoms. Whether, therefore, Ehrenberg’s genus, or Cresweliia, as proposed by Professor Walker-Arnott and myself, be pre- ferred, one portion of the Pywidicule may be regarded as satisfactorily disposed of. Two other genera of Pyaxidicuie—Pyxidicula and Dictyo- pyxis of Khrenberg-—still remain in a very confused state. In- deed, it is probable that the perfect condition of most of the species is unknown. Myr. Ralfs considered it desirable to re- tain Dictyopyw#is as a sub-genus or section of Pyxidicula, until some of the species were better known. His generic cha- racter for the whole is, “frustules simple or binately con- joined, free or adnate, bivalved; central portion obsolete ; valves very convex.’”’ The two sections bemg—1l. Frustules smooth, or minutely punctate (Pywidicula). 2. Frustules cellulose (Diciyopyzis). While recently engaged in the examination of Dr. Macrae’s slides, I was so fortunate as to find two examples of a Dictyopyxis with the frustules con- nected, and consequently I have it in my power to offer a more definite character of that genus, which will now be placed in as satisfactory a position as Creswellia. It remains to be seen, however, how many of the dia- toms at present referred to it will exhibit the same struc- ture. Diciyopyzis brevis, 0. sp., Grev.— Valves equal, cylindrical, much shorter than they are broad; junction-surfaces some- what convex; cellules hexagonal, very small, 10 in ‘001%. (PL TT, fie? Hab. Andaman Islands. Ceylon, Dr. Macrae. This species appears to differ very decidedly from those already described. It is remarkable for the shortness of the frustules; so that if one of the valves alone be taken, the length is scarcely more than half the breadth. ‘The cellules, small as they are, are exquisitely regular and hexagonal. The irustules are connected in the same manner as in Orihosira marina; only as the junction-surfaces are some- what convex instead of plane, they occupy less space. Side views of the valve are frequent. KUPODISCUS. Kupodiscus Jonesianus, n. sp., Grev.—Dise pale, with closely radiating lmes of minute puncta; processes oblong, submarginal. Breadth 0064”. (PI. II, fig. 3.) Hab. Guano; locality unknown; Dr. Macrae. A spécies remarkable for its minute structure, presenting in this respect the greatest possible contrast to EH. Argus ot Al dal GREVILLE, on New Diatons. 23 and HE. Rogersit. EH. radiatus of Bailey is, indeed, inter- mediate, but still very far removed from this very minutely punctate diatom. The processes are quite conspicuous, aud situated very close to the margin. The puncta in the centre of the disc are rather larger than the rest, but soon become minute and cover the whole surface with crowded, somewhat wavy lines, the wavy appearance being caused by the frequent dichotomous division of the lines of puncta. Immediately within the margin, and at short intervals, are a series of faint, inconspicuous, radiating lines, not longer than the processes themselves, which appear dark or light, according as they are focussed. They seem to be produced by a slight separation of the lines of puncta, the intervening part being somewhat thickened and prominent. AULACODISCUS. Aulacodiscus Macraeanus, u. sp., Grev.—-Processes cylin- drical-oblong, terminating inflated portions of the disc, which are rough, with large, raised points; smaller apiculi are numerously scattered over every other part of the surface except the spaces which alternate with those connected with the processes. Diameter ‘0054’. (Pl. II, fig. 4.) Hab. Ceylon; rare; Dr. Macrae. A slendid species, so like A. Peterse in general appearance that any diatomist might be excused for passing over it as such in a cursory examination. There are, nevertheless, very material differences. In the first place, the processes are not orbicular, asin A. Pefersii, but cylindrical-oblong. In the last-named species they are much nearer the margin, and the inflations vastly more prominent and elongated. Then there is a great difference in the margin itself. There is, indeed, what may, in general appearance, be called a double margin in both; the inner one being a continuation of the disc-surface, and striated, and an outer, narrow ring, which in 4. Petersii has a hazy, punctate character at the extreme edge, arising probably from an undulation in the silicious structure. Mr. Tuffen West has represented this in his figure of Mr. Shadbolt’s Hupodiscus crucifer (‘ Mic. Trans.,’ vol. ui, pl. i, fig. 12), which is admitted to be identical with A. Petersit, In A. Macraeanus this feature is wholly wanting. Then, again, a careful ex- amination of a series of A. Petersit shows that the raised points on the surface of the disc are confined to the inflations, and ‘less conspicuously along the connecting furrows and about the umbilicus.’ So far, however, is this from being 24s GrRrEVILLE, ov New Diutoms: the case in A. Macraeanus, there is no part uncovered by these apiculi, except the roundish intervals between the process-bearing spaces, and they are particularly numerous, as will be seen by referring to the figure, all round the margin. | In the above remarks I have referred only to A. Peters as occurring in South Africa. Australian specimens I have never seen, but through the kindness of Professor Walker- Arnott I possess a disc of the so-called New Zealand variety of which Mr. Raifs remarks (‘ Pritch. Infus., p. 843) that specimens from that quarter “have the granules and mark- ings more distinct and the JInflations smaller, less definite, and further from the margin.” It unfortunately happens that the dise in question has the concave surface uppermost, so that I cannot obtain a clear view of the processes. Their position, however, agrees with my proposed new species, so does the margin ; and the SUBIAES, as far as I can see it, is covered with raised points, as in my Ceylon specimens. I gladly appropriate Dr. Macrae’s name to this diatom, as, perhaps, the finest and most interesting thing in the collection he has kindly piaced in my cabinet. Aulacodiscus Jonesianus, n. sp., Grev.—Dise very large, somewhat lurid, with minute radiating granules, and a marginal belt of minute scattered apiculi; processes small, oblong, submarginal, the connecting furrows inconspicuous. Diameter -0110", (PL. II, fig. 5.) Hab. Guano; locality unknown; Dy. Macrae. A very fine and large species. The surface is filled up with minute granules, which at first sight seem all equal in size, but on a careful inspection are found to diminish insensibly towards the circumference. At the margin they become rapidly smaller, beg about 15 m-001”. There is no perceptible umbilicus, and the furrows are so conspicuous that they are scarcely to be perceived, except by commencing at the processes and directing the eye along the two series of granules of which they are composed. Near the processes the two-series of granules slightly diverge, and then leave a small, subtriangular, hyaline space. The processes are situ- ated at less than their own length from the margin. Minute apiculi, similar to those which. oceur in A. Petersi and scaber, are in this species confined to a marginal space equal to about a fourth of the radius. I have much pleasure m dedicating this noble diatom to Professor Jones, of the Calcutta University, who is asso- ciated with Dr. Macrae in = Inv estigation of Indian Diatom- ACER, | awe Ct GREVILLE, G1 New Dealoins. AULISCUS. Auliscus Peruvianus (Witton), Grev.—Valve orbicular, with close, radiating lines of fine puncta, some of them curved aud converging towards two small, fiat, circular, submarginal processes, each of which 1s surrounded by a circlet of minute apiculi; the margin is furmshed with a close row of larger apiculi. Diameter “0039”. (PI. II, fig. 6.) Hab. Peruvian guano, Dr. Macrae. The genus of this diatom is considered doubtful by my friend, Mr. Ralfs, who remarks (‘ Pritch. Infus.,’ p. 9388) that it has some resemblance to an duliscus, but that the puncta are not in flexuose lines. Fine specimens, however, which have come under my own observation, really confirm Mr. Ralfs’ first impression, having the centre connected with the processes by a rather narrow band of curved lines, not very conspicuous certainly, on account of the fine puncta. These curved or converging lines, taken in connexion with the imperforate, discoid processes, lead me to follow out Mr. Ralfs’ indication, and to refer it without question to Auliscus. The species is well marked by the numerous warginal apiculi and circlet of minute ones which surround the processes. 5;th of an mch—the two and a half millionth part of an inch. wee Lord’s Prayer, too, has been written and may be read in 555'5,5th of an English square inch. The measurements of one of these specimens were verified by Dr. Bowerbank, with a difference of not more than one five-millionth of an inch, and that difference, small as it 18, arose from his not including the prolongation of the letter f in the sentence, ‘ Deliver us from evil;”? so that he made the area occupied by the writing less than that stated above. Some idea of the minuteness of the characters in these specimens may be obtained from the statement that the whole Bible and Testament in writing of the same size might be placed twenty-two times on the surface of a square inch. The grounds for this startling assertion are as follows :—The Bible and Testament together, in the English language, are said to contain 3,566,480 letters. The number of letters in the Lord’s Prayer, as written, ending with the sentence, “ De- liver us from evil,” is 223, whence, as 375664 ®°=15,992, it appears that the Bible and Testament together contain the same number of letters as the Lord’s Prayer written 16,000 times ; if, then, the prayer were written in +5/5pth of an inch, the Bible and Testament in writing of the nate size would be contained by one square ees but as 35;!55cth of an inch is less than =':nd part of -;1,, nd of an inch, it follows that the Bible and Peamenaa in writing of that size would occupy less space than '-nd of a square inch; in other words, the writing is so small, that in similar characters the Bible and Testament together could be written twenty-two times in the space of one English square inch. To return to the objects of the Society ; its founders con- templated not only “the promotion and diffusion of improve- ments in the optical and mechanical construction, and in the The President’s Address. Felt mode of application of the microscope ;” but, also, 6 “ the ex- hibition of new or interesting microscopical objects and pre- parations,” and, « the advancement of science by encouraging ““communications and discussions relating to subjects of microscopical observation.” 6. The annual soireé provides both occasion and induce- ment to exhibit ‘‘ new or interesting microscopical objects and preparations.” It was held last year on the 10th of April, when the Council were gratified by the assemblage of upwards of 700 ladies and gentlemen who honoured them by accepting their invitation. For the success of that meeting our grate- ful acknowledgments are due to the Council of King’s College for the facilities afforded us, and for their kindness in permit- ting us the use of their noble hall for the occasion. For the complete and satisfactory arrangement of all the details, we are indebted to our esteemed Secretary, Mr. Blenkins, and his kind and attentive assistant, Mr. Williams. «. Ordinary meetings.—Besides the anniversary meeting, and the soireé, seven ordinary meetings have been held as usual, at which we have had ‘ communications and discussions relating to subjects of microscopical observations,’ &c. At all our meetings, I am glad to report, we were well supplied with papers. A. Four refer to the construction of the microscope and its accessories. 1. “ Description of the Universal Achromatic Microscope,” by Mr. R. Beck. (Read, October 9th, 1861. ‘Tyr. Mic. soe, Mond...” mes., vol: x,p. 11). The mstrument here described is not brought mto com- petition with the first-rate and costly instruments of the same or other makers. It is emphatically a cheap instrument. It is gratifying to find our makers of first-class microscopes seriously endeavouring to produce an instrument to be sold at a price which will be within the means of the many who are “‘earnestly seeking the entertainment and instruction afforded by a microscope of even moderate powers.” The more our means of observation are multiplied and brought within reach of a larger class of observers, the more rapidly may we expect to extend our knowledge and become ac- quainted with “that immense field of nature still unex- plored.”’ 2. “ Description of a microscope by Benjamin Martin,” by Mr. Williams. (Read, 8th January, 1862). fine The President’s Address. This instrument, so fully described by Mr. Willams, is in striking contrast with the small but effective instrument just noticed ; it is, however, in all respects a remarkable pro- duction, whether considered with regard to the many in- genious contrivances, or the excellence of the workmanship shown in its construction. 3. For the effective use of the microscope, improved methods of illumination have been proved to be of not less importance than improved objectives. On this subject we have been favoured with a communication by the Rev. J. B. Reade. “On a new Hemispherical Condenser for the Micro- scope, and its use in illustratmg an important principle in Microscopic Illumination.” (Read, 8th May, 1861. ‘Tr. Mic. Soc. Lond.,’ n. s., vol. ix, p. 59). “The principle sought to be carried out is to throw the axis of the pencil of illuminating rays in a direction at right angles to the line to be resolved.”” The author shows how, by the use of a simple lens, and a few diaphragms with apertures at their circumference, two or more illuminating pencils may be thrown at the same time upon an object having two or more sets of lines, and the direction of the axis of the pencil be determined by the position of the apertures on the margin of the diaphragm. The arrangement is simple, cheap, and easy of adjustment; its efficiency was placed beyond doubt by the most conclusive of all proofs, actual demonstration. 4. “On a Portable Revolving Table,’ by J. Burton, Esq. (Read, 9th October, 1861. ‘Tr. Mic. Soc. Lond., n.s., vol. x, p. 9). This falls under the head of “ arrangements for affording increased facilities for the use of the microscope.” It is a simple and ingenious contrivance for enabling an exhibitor to submit an object to several persons seated at the same table with the least possible disturbance. ‘The table was exhibited at the meeting, and woodcuts of it are published m ‘The Transactions.’ The contrivance appears to be well calculated to accomplish the design. B. On Crystallography.—This paper well illustrates the in- fluence of improvements in the construction of the microscope. It is “On the Microscopic Characters of the Crystals of Arsenious Acid,” by William A. Guy, M.B., Cantab., Profes- sor of Forensic Medicine, King’s College, London. (Read, 8th May, 1861. ‘Tr. Mic. Soc. Lond.,’ n. s., vol. ix, p. 50). We must all admire the skill manifested in explaining the phases of the octohedron, to which form most, if not all, of The President’s Address. 70 the varied forms observed are referred. The existence of twin crystals, and the not unfrequent occurrence of a “ half crystal” are satisfactorily established, and we are taught how many of the apparently aberrant forms may be explained by considering them as phases of the half crystal; the existence of crystals other than octohedra is also distinctly announced. All that relates to the characters of arsenious acid is of high interest from the grave questions which are frequently in- volved in medico-legal investigations of which it is the subject. Regarded from this point of view, I think this com- munication fairly deserves to be considered the most impor- tant and most interesting of the many interesting papers of the year. Youall, I am sure, have much satisfaction at now being able to reckon its learned author among the members of the Microscopical Society. The author assures us that one of his objects in presenting this paper was to show “ bya striking instance the great value of the binocular microscope as a means of diagnosis,” and in summing up the results of his inquiries, gives important testimony to its usefulness. He remarks :—“I felt that my views concerning the large part played by the half crystal, though highly probable, were still only probable; but under the binocular microscope all my doubts were dissipated, my errors corrected, some surmises confirmed, and most of my inferences justified.” He adds :— “Tf there is any one who doubts the value of this form of microscope, or is disposed to treat it simply as a philosophical toy, I would ask him to examine these crystals with the monocular instrument by transmitted light, and with the binocular instrument by reflected light ;’-—“ the fine relief and perfect roundness of the tube and its contents is at one and the same time a proof of the utility and faithfulness of the binocular microscope.” c. On Zoology. 1. “On the Circulation in the Tadpole,” by W. U. Whitney, Esq. (Read June 13th, 1861. ‘Tr. Mic. Soc. Lond.,’ n. s., mou, %. 1p. |). In this paper we have additional testimony to the value of the binocular microscope, applied to investigations in a widely different field of research. 2. “On the Metamorphoses of a Coccus found upon Oranges,” by Richard Beck. (Read March 138th, 1861. ‘Tr. Mie. Soc. Lond.’ n. s., vol. 1x, p. 47). The author describes the development of a species of coccus found under the shield commonly met with on the sweet or- anges sold in the shops; they are not so common on the fruit sold in the streets. 'To those who propose to take advantage 74 The President’s Address. of the season when oranges are plentiful to pursue this inves- tigation, | would recommend attention to the suggestion of the Rev. Mr. Reade, viz., immersion of the shield for a short time in hot liquor potassee, by which the vegetable portion is dissolved, while the animal part remains, and the insect in all its stages of development is distinctly revealed. The author concludes with this remark :—“» ~. jastuosa, Ehr., 18 4 Macraena, Grev., 20. dt Table, John Burton on a portable revolving, 9, Tadpole, W. U. Whitney on thie circulation in the, 1. Triceratium, 92. convexum, Grev., 27. decorum, Grev., 92. flexuosum, Grev., 93. inornutum, Grev., 94. orbiculatum, Shadb., 28. pectinatum, Grev., 92. Roperianum, Grev., 93. és Thwaitesianum, Grev., 28. W. R Whitney, W. U., on the circulation in the tadpole, ile Williams, Jolin, some account of the Martin microscope, 31]. he 5 > ax age rf: 2 Abe ot SMITHSONIAN INSTITUTION LIBRARIES win